It's official: Facebook isn't cool. Though some teens still use it, they prefer to use a variety of apps to connect, curate, and capture their lives in different ways. And though household names such as Instagram, Snapchat, and Twitter have proven their staying power, teens love to try out new apps they hear about from friends, ads, or even what's trending in the app store.

This can be challenging for parents to keep up with. But you don't need to know all the ins and outs of all the apps, sites, and terms that are "hot" right now (and frankly, if you did, they wouldn't be trendy anymore). But knowing the basics -- what they are, why they're popular, and what problems can crop up when they're not used responsibly -- can make the difference between a positive and a negative experience for your kid.

Below, we've laid out some of the most popular types of apps and websites for teens: texting, microblogging, livestreaming, self-destructing/secret, and chatting/meeting/dating. The more you know about each, the better you'll be able to communicate with your teen about safe choices.

The bottom line for most of these tools? If teens are using them respectfully, appropriately, and with a little parental guidance, they're mostly fine. So take inventory of your kids' apps and review the best practices.

TEXTING APPS

GroupMe is an app that doesn't charge fees or have limits for direct and group messages. Users also can send photos, videos, and calendar links.

What parents need to know

It's for older teens. The embedded GIFs and emojis have some adult themes, such as drinking and sex.

The embedded GIFs and emojis have some adult themes, such as drinking and sex. Teens are always connected. Without fees or limits, teens can share and text to their heart's content, which may mean they rarely put the phone down.

Kik Messenger is an app that lets kids text for free. It's fast and has no message limits, character limits, or fees if you only use the basic features. Because it's an app, the texts won't show up on your kid's phone's messaging service, and you're not charged for them (beyond standard data rates).

What parents need to know

Stranger danger is an issue. Kik allows communication with strangers who share their Kik usernames to find people to chat with. The app allegedly has been used in high-profile crimes, including the murder of a 13-year-old girl and a child-pornography case.

Kik allows communication with strangers who share their Kik usernames to find people to chat with. The app allegedly has been used in high-profile crimes, including the murder of a 13-year-old girl and a child-pornography case. It's loaded with covert marketing. Kik specializes in "promoted chats" -- basically, conversations between brands and users. It also offers specially designed apps (accessible only through the main app), many of which offer products for sale.

WhatsApp lets users send text messages, audio messages, videos, and photos to one or many people with no message limits or fees.

What parents need to know

It's for users 16 and over. Lots of younger teens seem to be using the app, but this age minimum has been set by WhatsApp.

Lots of younger teens seem to be using the app, but this age minimum has been set by WhatsApp. It can be pushy. After you sign up, it automatically connects you to all the people in your address book who also are using WhatsApp. It also encourages you to add friends who haven't signed up yet.

Discord started as a place for gamers to chat while playing video games but has become a bigger platform where users can use text, voice-chat, and video-chat to discuss a wide variety of topics.

What parents need to know

There are public and private "servers" or discussion groups. Teens can join public groups, ask to join private ones, or start their own. The safest option is for them to join a private group with people they know in real life.

Some groups are more moderated than others, some are NSFW, and some are hate-filled. There are plenty of groups that are meant for adults only, and some are totally tame and well moderated. If your kid is in one of the latter, the risk is much lower.

PHOTO AND VIDEO-SHARING APPS AND SITES

Instagram lets users snap, edit, and share photos and 15-second videos, either publicly or within a private network of followers. It unites the most popular features of social media sites: sharing, seeing, and commenting on photos. It also lets you apply fun filters and effects to your photos, making them look high-quality and artistic.

What parents need to know

Teens are on the lookout for "likes." Similar to the way they use Facebook, teens may measure the "success" of their photos -- even their self-worth -- by the number of likes or comments they receive. Posting a photo or video can be problematic if teens are posting to validate their popularity.

Similar to the way they use Facebook, teens may measure the "success" of their photos -- even their self-worth -- by the number of likes or comments they receive. Posting a photo or video can be problematic if teens are posting to validate their popularity. Public photos are the default. Photos and videos shared on Instagram are public unless privacy settings are adjusted. Hashtags and location information can make photos even more visible to communities beyond a teen's followers if his or her account is public.

Photos and videos shared on Instagram are public unless privacy settings are adjusted. Hashtags and location information can make photos even more visible to communities beyond a teen's followers if his or her account is public. Kids can send private messages. Instagram Direct is like texting with photos or videos and you can do it with up to 15 mutual friends. These pictures don't show up on their public feeds. Although there's nothing wrong with group chats, kids may be more likely to share inappropriate stuff with their inner circles.

Tik Tok - Real Short Videos is a performance- and video-sharing social network that mostly features teens lip-synching to famous songs but also includes some original songwriting and singing. Users can build up a following among friends or share posts publicly.

What parents need to know

Songs and videos contain lots of iffy content. Because the platform features popular music and a mix of teen and adult users, swearing and sexual content are commonplace.

Because the platform features popular music and a mix of teen and adult users, swearing and sexual content are commonplace. There are often creepy comments. Though lots of comments are kind, videos often have comments about the performer's body or other sexual references, and since kids under 13 and adults use the app, it's especially creepy.

Though lots of comments are kind, videos often have comments about the performer's body or other sexual references, and since kids under 13 and adults use the app, it's especially creepy. Gaining followers and fans feels important. Teens want a public profile to get exposure and approval, and many are highly motivated to get more followers and likes for their videos.

MICROBLOGGING APPS AND SITES

Tumblr is like a cross between a blog and Twitter: It's a streaming scrapbook of text, photos, and/or video and audio clips. Users create and follow short blogs, or "tumblogs," that can be seen by anyone online (if they're made public). Many teens have tumblogs for personal use: sharing photos, videos, musings, and things they find funny with their friends.

What parents need to know

Porn is easy to find. This online hangout is hip and creative but sometimes raunchy. Pornographic images and videos and depictions of violence, self-harm, drug use, and offensive language are easily searchable.

This online hangout is hip and creative but sometimes raunchy. Pornographic images and videos and depictions of violence, self-harm, drug use, and offensive language are easily searchable. Privacy can be guarded but only through an awkward workaround. The first profile a member creates is public and viewable by anyone on the internet. Members who desire full privacy have to create a second profile, which they're able to password-protect.

The first profile a member creates is public and viewable by anyone on the internet. Members who desire full privacy have to create a second profile, which they're able to password-protect. Posts are often copied and shared. Reblogging on Tumblr is similar to re-tweeting: A post is reblogged from one tumblog to another. Many teens like -- and, in fact, want -- their posts to be reblogged.

Twitter is a microblogging tool that allows users to post brief, 140-character messages -- called "tweets" -- and follow other users' activities. It's not only for adults; teens like using it to share tidbits and keep up with news and celebrities.

What parents need to know

Public tweets are the norm for teens. Though you can choose to keep your tweets private, most teens report having public accounts. Talk to your kids about what they post and how a post can spread far and fast.

Though you can choose to keep your tweets private, most teens report having public accounts. Talk to your kids about what they post and how a post can spread far and fast. Updates appear immediately. Even though you can remove tweets, your followers can still read what you wrote until it's gone. This can get kids in trouble if they say something in the heat of the moment.

LIVE-STREAMING VIDEO APPS

Houseparty - Group Video Chat is a way for groups of teens to connect via live video. Two to eight people can be in a chat together at the same time. If someone who's not a direct friend joins a chat, teens get an alert in case they want to leave the chat. You can also "lock" a chat so no one else can join.

What parents need to know

Users can take screenshots during a chat. Teens like to think that what happens in a chat stays in a chat, but that's not necessarily the case. It's easy for someone to take a screenshot while in a chat and share it with whomever they want.

Teens like to think that what happens in a chat stays in a chat, but that's not necessarily the case. It's easy for someone to take a screenshot while in a chat and share it with whomever they want. There's no moderator. Part of the fun of live video is that anything can happen, but that can also be a problem. Unlike static posts that developers may review, live video chats are spontaneous, so it's impossible to predict what kids will see, especially if they're in chats with people they don't know well.

Live.me – Live Video Streaming allows kids to watch others and broadcast themselves live, earn currency from fans, and interact live with users without any control over who views their streams.

What parents need to know

It's associated with Tik Tok - including musical.ly. Because of the parent app's popularity, this streamer is very popular, and many kids who use one app use the other, too.

Because of the parent app's popularity, this streamer is very popular, and many kids who use one app use the other, too. Kids can easily see inappropriate content. During our review, we saw broadcasters cursing and using racial slurs, scantily clad broadcasters, young teens answering sexually charged questions, and more.

During our review, we saw broadcasters cursing and using racial slurs, scantily clad broadcasters, young teens answering sexually charged questions, and more. Predatory comments are a concern. Because anyone can communicate with broadcasters, there is the potential for viewers to request sexual pictures or performances or to contact them through other social means and send private images or messages.

YouNow: Broadcast, Chat, and Watch Live Video is an app that lets kids stream and watch live broadcasts. As they watch, they can comment or buy gold bars to give to other users. Ultimately, the goal is to get lots of viewers, start trending, and grow your fan base.

What parents need to know

Kids might make poor decisions to gain popularity. Because it's live video, kids can do or say anything and can respond to requests from viewers -- in real time. Though there seems to be moderation around iffy content (kids complain about having accounts suspended "for nothing"), there's plenty of swearing and occasional sharing of personal information with anonymous viewers.

Because it's live video, kids can do or say anything and can respond to requests from viewers -- in real time. Though there seems to be moderation around iffy content (kids complain about having accounts suspended "for nothing"), there's plenty of swearing and occasional sharing of personal information with anonymous viewers. Teens can share personal information, sometimes by accident. Teens often broadcast from their bedrooms, which often have personal information visible, and they sometimes will share a phone number or an email address with viewers, not knowing who's really watching.

Teens often broadcast from their bedrooms, which often have personal information visible, and they sometimes will share a phone number or an email address with viewers, not knowing who's really watching. It's creepy. Teens even broadcast themselves sleeping, which illustrates the urge to share all aspects of life, even intimate moments, publicly -- and potentially with strangers.

SELF-DESTRUCTING/SECRET APPS

Snapchat is a messaging app that lets users put a time limit on the pictures and videos they send before they disappear. Most teens use the app to share goofy or embarrassing photos without the risk of them going public. However, there are lots of opportunities to use it in other ways.

What parents need to know

It's a myth that Snapchats go away forever. Data is data: Whenever an image is sent, it never truly goes away. (For example, the person on the receiving end can take a screenshot of the image before it disappears.) Snapchats can even be recovered. After a major hack in December 2013 and a settlement with the FTC, Snapchat has clarified its privacy policy, but teens should stay wary.

Data is data: Whenever an image is sent, it never truly goes away. (For example, the person on the receiving end can take a screenshot of the image before it disappears.) Snapchats can even be recovered. After a major hack in December 2013 and a settlement with the FTC, Snapchat has clarified its privacy policy, but teens should stay wary. It can make sexting seem OK. The seemingly risk-free messaging might encourage users to share pictures containing sexy images.

The seemingly risk-free messaging might encourage users to share pictures containing sexy images. There's a lot of iffy, clicky content. Snapchat's Discover feature offers a grab-bag of articles, videos, and quizzes from magazine publishers, TV networks, and online sources mostly about pop culture, celebrities, and relationships (a typical headline: "THIS is What Sex Does To Your Brain").

Whisper is a social "confessional" app that allows users to post whatever's on their minds, paired with an image. With all the emotions running through teens, anonymous outlets give them the freedom to share their feelings without fear of judgment.

What parents need to know

Whispers are often sexual in nature. Some users use the app to try to hook up with people nearby, while others post "confessions" of desire. Lots of eye-catching, nearly nude pics accompany these shared secrets.

Some users use the app to try to hook up with people nearby, while others post "confessions" of desire. Lots of eye-catching, nearly nude pics accompany these shared secrets. Content can be dark. People normally don't confess sunshine and rainbows; common Whisper topics include insecurity, depression, substance abuse, and various lies told to employers and teachers.

People normally don't confess sunshine and rainbows; common Whisper topics include insecurity, depression, substance abuse, and various lies told to employers and teachers. Although it's anonymous to start, it may not stay that way. The app encourages users to exchange personal information in the "Meet Up" section.

CHATTING, MEETING, AND DATING APPS AND SITES

Monkey -- Have Fun Chats. If you remember Chatroulette, where users could be randomly matched with strangers for a video chat, this is the modern version. Using Snapchat to connect, users have 10 seconds to live video-chat with strangers.

What parents need to know

Lots of teens are using it. Because of the connection with Snapchat, plenty of teens are always available for a quick chat -- which often leads to connecting via Snapchat and continuing the conversation through that platform.

Because of the connection with Snapchat, plenty of teens are always available for a quick chat -- which often leads to connecting via Snapchat and continuing the conversation through that platform. Teens can accept or reject a chat. Before beginning a chat, users receive the stranger's age, gender, and location and can choose whether to be matched or not.

MeetMe: Chat and Meet New People. The name says it all. Although not marketed as a dating app, MeetMe does have a "Match" feature whereby users can "secretly admire" others, and its large user base means fast-paced communication and guaranteed attention.

What parents need to know

It's an open network. Users can chat with whomever's online, as well as search locally, opening the door to potential trouble.

Users can chat with whomever's online, as well as search locally, opening the door to potential trouble. Lots of details are required. First and last name, age, and ZIP code are requested at registration, or you can log in using a Facebook account. The app also asks permission to use location services on your teens' mobile devices, meaning they can find the closest matches wherever they go.

Omegle is a chat site that puts two strangers together in their choice of a text chat or a video chat. Being anonymous can be very attractive to teens, and Omegle provides a no-fuss way to make connections. Its "interest boxes" also let users filter potential chat partners by shared interests.

What parents need to know

Users get paired up with strangers. That's the whole premise of the app. And there's no registration required.

That's the whole premise of the app. And there's no registration required. This is not a site for kids and teens. Omegle is filled with people searching for sexual chat. Some prefer to do so live. Others offer links to porn sites.

Omegle is filled with people searching for sexual chat. Some prefer to do so live. Others offer links to porn sites. Language is a big issue. Since the chats are anonymous, they're often much more explicit than those with identifiable users might be.

Yubo (formerly Yellow - Make new friends) is an app that is often called the "Tinder for teens" because users swipe right or left to accept or reject the profiles of other users. If two people swipe right on each other, they can chat and hook up via Snapchat or Instagram.

What parents need to know

It's easy to lie about your age. Even if you try to enter a birth date that indicates you're under 13, the app defaults to an acceptable age so you can create an account anyway.

Even if you try to enter a birth date that indicates you're under 13, the app defaults to an acceptable age so you can create an account anyway. You have to share your location and other personal information. For the app to work, you need to let it "geotag" you. Also, there are no private profiles, so the only option is to allow anyone to find you.

For the app to work, you need to let it "geotag" you. Also, there are no private profiles, so the only option is to allow anyone to find you. It encourages contact with strangers. As with Tinder, the whole point is to meet people. The difference with Yellow is that the endgame is sometimes just exchanging social media handles to connect there. Even if there's no offline contact, however, without age verification, teens are connecting with people they don't know who may be much older.

Amino - Communities, Chat, Forums, and Groups is an interest-based app that lets users find people who are into the same things. Teens can join groups -- or create them -- and then post within the group, follow other users, and chat with them via text, voice, or video.

What parents need to know

Contact with strangers is part of the experience . While it's great for kids to be able to feel a sense of belonging and kinship with others, the mix of kids and adults blended with all varieties of chat makes it risky. Also, unless a kid is in a closed group, everything they post is public, and other users can search for them. Make sure your kid's location is not included in their profile.

. While it's great for kids to be able to feel a sense of belonging and kinship with others, the mix of kids and adults blended with all varieties of chat makes it risky. Also, unless a kid is in a closed group, everything they post is public, and other users can search for them. Make sure your kid's location is not included in their profile. Mature content and bullying is common . Since each community makes its own rules, profanity, sexual references, and violent content are a part of some forums. A lot of what your kid sees, who they meet, and what people post is determined by the groups they decide to join, as some are very tame and some are definitely not for kids.

. Since each community makes its own rules, profanity, sexual references, and violent content are a part of some forums. A lot of what your kid sees, who they meet, and what people post is determined by the groups they decide to join, as some are very tame and some are definitely not for kids. It's not made with kids in mind. Because this app wasn't created for kids, it doesn't have the same safeguards or privacy standards as apps that are made for kids.

The bottom line for most of these tools? If teens are using them respectfully, appropriately, and with a little parental guidance, they should be fine. Take inventory of your kids' apps and review the best practices.

TV senior editor Polly Conway and former Common Sense Education writer Kelly Schryver contributed to this article.