If you’re old enough to remember Kesha’s “Tik Tok,” you may not be “old” by the standard definition—the song only came out in 2009—but you’re probably still too old to know about the other TikTok, the app of the same name. Teenagers and young people are the primary users of the app, which can loosely be described as a social network for amateur music videos (users can make their own as well as just watch everyone else’s). If you know about it at all, it might be by its former name, Musical.ly. So why is it called something else now? What distinguishes it from the other apps that teens are obsessed with? Is it really worth a billion dollars? And are amateur music videos any good? The answers to those and more questions can be found below in this guide to TikTok, designed specifically for all those people who have never done the #raindropchallenge, the #posechallenge, or, clearly, the #levelupchallenge.

What was Musical.ly, and why did it change its name to TikTok?

Musical.ly launched in 2014 (it was founded by Chinese entrepreneurs Alex Zhu and Luyu Yang) and gained a dedicated userbase over the next few years; in November 2017 it was acquired by ByteDance, a Beijing-based media and tech company, for a reported $1 billion. At the time, ByteDance already owned a similar app, TikTok, which had launched in China in 2016. Musical.ly and TikTok were both popular, but each reigned in different parts of the world, according to Reuters—the former in the Americas and Europe with 100 million monthly active users (who called themselves “Musers”—it’s unclear if that name will survive), and the latter in Asia with 500 million of the same. In fact, TikTok was also the most downloaded iOS app in the first quarter of this year, per market research. ByteDance’s decision to bring the two apps together as one product was a move toward efficiency, and the company told Reuters it decided that TikTok “better reflects the breadth of content created on our platform that extends beyond music to comedy, performance art and more.” So, in early August, TikTok absorbed Musical.ly—all user accounts and videos were moved to TikTok, and the app formerly known as Musical.ly ceased to exist. (Due to China’s restrictive internet rules, TikTok remains a standalone app there, where it goes by the name Douyin and has over 300 million monthly active users.)

What else changed when the app became TikTok?

Not all that much! The update notes promised “new creator tools and interactive filters” as well as “bug fixes and performance improvements.” These include the ability to post “reactions,” new filters, and background effects. Users were additionally promised access to content from more countries and better personalized recommendations. And since digital mindfulness is all the rage right now, the new app is able to warn users when they’ve been using it for more than two hours.

In a video reviewing the new app, YouTuber LifeWithErick noted that the old Musical.ly app indicated in profiles how many videos users had on the site and how many videos they had liked, features that disappeared with the update. The camera, the font, and the way drafts appear are also different.

How long are TikTok videos?

Like the dearly departed app Vine, Musical.ly encouraged creativity within very specific limits. Rather than the 6 seconds that defined Vine, on Musical.ly, and now TikTok, 15 seconds is the magic number. That’s the upper limit for recording within the app, but users can string those clips together to make stories of up to 60 seconds long. Users also have the option of uploading longer videos that were not recorded within the app.

What do people do on TikTok? Is it all lip-synching?

Lip syncs were the original raison d’être of Musical.ly, but the app came to be known for more than just music. (“2017 will be remembered as the year Musical.ly transitioned from an app primarily for posting music videos to a broader social-media and entertainment platform,” the Wall Street Journal wrote in November.) The choice to go with the TikTok platform means that will only be more true going forward.

Dancing is particularly big on the app, which makes sense given its musical roots, and so are other movement-based activities like gymnastics, cheerleading, and parkour. Comedy is huge, though it’s often lip-sync–based comedy, which is something better experienced than explained: Here is a video of a girl lip-synching to the viral “catch me outside” clip from the episode of the Dr. Phil show that gave us rapper Bhad Bhabie. Also on the app, media companies like NBCUniversal and Seventeen host short “shows” that are aimed at its young users. Basically, you can find a little bit of everything there.

How does one navigate TikTok?

Like videos from Vine and Instagram Stories and as befitting a mobile-native app, TikTok videos are vertical. That’s not the only element of the app that might ring familiar—there are filters à la Snapchat, and you can show appreciation through “hearts,” which are essentially the same as “likes.” The app should seem pretty intuitive if you’ve logged time elsewhere in the social media–verse.

You’ve surely heard of the #InMyFeelingsChallenge, the dance craze based on the Drake song. On TikTok, that’s just the beginning.

After you download TikTok and open it on your phone, a video will start playing right away without you even selecting one (just like in IGTV). The videos that play automatically are featured videos, labeled “for you,” which the app has chosen to highlight—users can switch to “following” to see videos from the people they follow—maybe you’ll follow friends, or popular “Musers,” or just people who amuse you. Clicking on the home button in the bottom left corner will load up a new video.

To explore further, try the magnifying glass icon next to the home icon, where you can search key words and hashtags—yes, TikTok uses hashtags—as well as explore some of what’s trending—yes, there’s also trending in TikTok. Within videos, tap on the screen to pause (as with Instagram Stories), and look to the right side for the user icon of the video’s creator (which will take you to that user’s profile), the number of “hearts” it got (you can click to heart it too), and the number of comments it got (click to read them). Along the bottom of the video, find the user’s name, caption, and the name of the song that’s playing. Captions tend to contain more hashtags that you can explore by clicking on them. TikTok has a library full of clips of popular songs, but users can also use their own recordings or “original sound,” which can be anything from the person talking to a different excerpt of a song to a strange viral earworm. You can click on any song to see more videos of that song.

When you’re ready to post your own video, click on the plus sign at the bottom of the home screen—and study up on how to make a good one.

Is TikTok only for teens and young people? Will so-called olds understand it?

As mentioned above, if you’ve used basically any other form social media, you should have a pretty good head start. That said, it’s true that the app’s userbase is quite young: Earlier this year, Digiday cited the statistic that 50 percent of those who used Musical.ly on iPhones were between the ages of 13 and 24; that number was 60 percent on Android. (Female users outnumber males on both platforms.) Anecdotally, the app is also quite popular with tweens as well, despite terms of service that state that users must be at least 13 to sign up.

Is TikTok wholesome and safe? Are there creeps?

As with any social network, there have been instances of strange adults contacting children inappropriately on the app. Parents have access to the usual privacy settings if they’re concerned about their kids’ accounts, though there are no parental controls. Also, remember: It’s possible to watch videos without ever creating an account.

As for the appropriateness of the content itself, all the bad words and sexual lyrics that go along with popular music are obviously part of the app, and some of the outfits and dance moves in videos can be a little risqué. There have also been some reports of darker content, like videos depicting self-harm and violence, on the app.

Has anyone gotten famous from TikTok/Musical.ly?

Yes, much like YouTube and Instagram, it has its own ecosystem of stars, some of whom have followings of millions of fans. Top Musers include Baby Ariel, Jacob Sartorius, Loren Gray, twins Lisa and Lena (twins are big on TikTok), and Mackenzie Ziegler (younger sister of Sia’s favorite young collaborator Maddie), among others.

Can people make money on TikTok?

In short, yes! Music labels can make money when popular videos lead to increased sales and streams, brands can make money through partnerships with the app, and individual Musers can make money, too: Fans or followers can purchase monetary gifts of anywhere from 5 cents to $50 for Musers, with a percentage of the revenue also going to the app itself and the distributor, like Apple or Google. These creators can pursue “brand partnerships” as well. One Muser was reportedly earning $25,000 a month through partnerships and gifts as of last year.

What’s with all the challenges?

You’ve surely heard of the #InMyFeelingsChallenge, the dance craze based on the Drake song. On TikTok, that’s just the beginning. At any given time, you can peruse at least five different challenges that are trending on the app, where “challenge” has come to mean a format for a video for fans to endlessly iterate upon, usually involving a song. The #idolchallenge asks fans to dance to the new BTS song “Idol,” the #matildachallenge has fans making videos where they pretend they can do telekinesis (like in the ’90s movie), the #unmakeupchallenge is about taking off makeup, the #dontjudgemechallenge seems to be about dressing up in extremely ugly, clownish makeup and then transforming into a beautiful person—or (record scratch) not—and many, many more.

What about memes? Are there memes on TikTok?

Of course there are memes! Frequently there are challenge-esque hashtags that don’t explicitly include the word “challenge” in them, but they share DNA with the challenges nonetheless, which means it’s kind of difficult to distinguish between challenges and memes on TikTok, but it’s probably not something to spend too long dwelling on. Just know that for every meme you encounter outside of TikTok, you can probably find it within TikTok. For example, right now there’s a lot (like, more than 1 million) of videos based on that “Johny, Johny” song. There’s a lot of SpongeBob. In addition to the #InMyFeelingsChallege, there’s this whole submeme where girls mouth along to a track that answers “Kiki” with an annoyed “What?” and “Do you love me?” with “No!” Basically, TikTok is a world unto itself, one that’s very much worth exploring next time you find yourself with 15 seconds, or hell, 15 times that, to spare.