Not long ago we did a piece explaining what virtual reality was and what made it important. But what’s augmented reality?

“Virtual reality, as seen in the Oculus Rift or Project Morpheus, surrounds the user in a virtual experience like an immersive video game or a movie,” explains Eric Johnson in Re/code. “Augmented reality, as seen in Google Glass or Microsoft’s HoloLens, layers virtual information or graphics on top of the real world.”

And while virtual reality is expected to be popular in areas such as entertainment and training, augmented reality has the potential to be used even more widely, with companies such as Tesla and Facebook announcing significant research efforts. The advantage of augmented reality is that you can use it while you are out and about, while virtual reality is likely to be limited to use at home, Johnson writes.

Consequently, the digital M&A firm Digi-Capital has predicted the augmented reality market to be $120 billion—or four times the size of the not-inconsiderable virtual reality market, Johnson writes. Potential use cases include commerce, voice calls, Web browsing, film/TV streaming, enterprise apps, advertising, consumer apps, games and theme park rides, he writes. Similarly, Research and Markets predicts a CAGR of 37 percent in augmented reality between 2015 and 2020.

Tesla recently announced that it was hiring Milan Kovac, a former principal engineer at SKULLY, the creator of the first motorcycle helmet to come with heads-up display and an augmented reality camera. Speculation is that he will be working on a similar heads-up display for the upcoming Tesla 3 automobile, for which the company has already received nearly 400,000 pre-orders and which has a fairly minimalist dashboard.

Facebook, which purchased virtual reality maker Oculus VR about two years ago, also discussed its plans for augmented reality at its recent developers conference. “In the future [on the order of ten years], people will be able to show photos to friends wearing hybrid VR and AR glasses, and expand those pictures in front of their friends’ faces,” writes Jonathan Vanian in Fortune.

“No more laptops. No more smartphones,” writes Ben Gilbert in Tech Insider. “Just a set of lightweight glasses that enable immersive virtual reality experiences as well as seamless augmented reality experiences—imagine wearing a pair of lightweight glasses that, in real time, allow you to see information about the world around you. Better still, that information is broadcast right into your field of view. You could look at the Statue of Liberty, for instance, and see a floating history of Lady Liberty all around her. You’d be the only one seeing it, because the information is only broadcast into your vision.”

Heck, augmented reality could even bring back Google Glass, as well as competitors.

Naturally, Facebook’s focus is going to be on using augmented reality in the context of social networking, but augmented reality can be used for many other functions as well. Right now, it’s used for things like putting smiley faces on cat videos, but more business-oriented functions will be likely (like, putting some other symbol on potential customers or shoplifters in a crowd video).

“What if when you arrive at a restaurant you see, overlaid in front of you, all the Facebook comments about the eatery? There’s even an aggregate sentiment meter,” writes Lance Ulanoff in Mashable. “Facebook AR could be a bonanza for businesses, as well, which could provide special offers when you arrive at the restaurant. You’d seen them in AR and then, maybe with a wink, add them to your Facebook mobile app.” Location-aware bots could appear in front of you, pointing you to the nearest Burger King and, at the airport, placing large arrows on the floor so you can find your way to your boarding gate, he adds.

“If virtual reality is The Matrix, then augmented reality is The Terminator,” writes The Economist. “Augmented reality does not dispense with the real world, but uses computers to improve it in various ways. In The Terminator, Arnold Schwarzenegger’s killer robot sees a constant stream of useful information laid over his view of the world, a bit like the heads-up displays used by fighter pilots.”

Or, using different movies as examples, “Think Tony Stark, the comic-book character who scans information-filled holograms beamed in front of his Iron Man mask, or John Anderton, the character that Tom Cruise played while flipping through digital screens floating in the air in Minority Report,” writes Michael Liedtke for the Associated Press.

Instead of using display screens and keyboards, users could navigate through an array of holographic screens suspended in front of their faces and controlled with the touch of their hands, with virtual keyboards for data entry, Liedtke writes. “People will be able to reach into their holographic screen, pull out a drawing of the human anatomy and remove the skeleton to study,” he predicts. “Or they might look inside a shoe they are thinking of buying. Phone calls will become obsolete as everyone in a conversation appears as holograms that can exchange documents and data.”

Other examples of augmented reality business use cases include:

VeinViewer , a medical device that projects images of a patient’s veins onto his skin, to help doctors better aim injections

, a medical device that projects images of a patient’s veins onto his skin, to help doctors better aim injections Word Lens , which translates between languages by looking at the world through a smartphone camera, recognizing text, and then presenting the user with a real-time image in which that text has been replaced by its equivalent in another language

, which translates between languages by looking at the world through a smartphone camera, recognizing text, and then presenting the user with a real-time image in which that text has been replaced by its equivalent in another language Microsoft’s HoloLens , which aims to liberate computing from a fixed screen by overlaying its users’ view with useful additions such as painting your email across a nearby wall or putting weather information on a breakfast table

, which aims to liberate computing from a fixed screen by overlaying its users’ view with useful additions such as painting your email across a nearby wall or putting weather information on a breakfast table An IKEA app that lets customers see what a particular piece of furniture would look like in their home

that lets customers see what a particular piece of furniture would look like in their home Excedrin has even developed an augmented reality app to show people what having a migraine was like

It’s not too soon to start thinking about augmented reality applications in your industry. After all, you don’t want it to be a headache later.