Virtual reality is a technology that has been around for decades - much like 3D - but thanks to developments in recent years, it's set to become a mainstream hit very soon indeed. Here's everything you need to know about virtual reality, including some of the headsets which you can buy right now.
What is virtual reality?
Although some people use the terms 'VR' and '3D' interchangeably, they shouldn't. Virtual reality creates a simulated environment - much like any 3D computer game - but also simulates your presence in that environment, so you see it from a first-person view.
The environment doesn't have to be fictional: virtual reality can be used for real environments, so you could take a guided tour of Buckingham Palace without leaving your bedroom.
Using a VR headset with sensors including accelerometers and gyroscopes, the movement of your head changes the images displayed on the headset's screens so you can look around the virtual 3D environment: you're not limited to a 'window on the world' that you get with a computer monitor or TV screen.
The headset aims to give you a similar field of view to natural eyesight, so your brain is effectively tricked into believing you're actually there.
Of course, virtual reality doesn't only involve sight. Headphones can reproduce audio from the virtual world, and some VR systems even have haptic feedback so you can feel it too.
Most VR headsets limit you to looking around only, but others can monitor your whole body using positional tracking. This allows you to walk around in the simulated environment, creating an even more immersive experience. There's no reason why smells can't be added, although that's not something we've seen in any current VR system.
The two types of VR headset
The best-known VR goggles are made by Oculus, but the Rift is only available to developers at the moment. The headset is likely to go on sale later this year, by which time developers should have had enough time to put games, apps and other software together to make the Rift useful.
The googles connect to a PC, which generates the virtual environments: they're not a standalone device. Currently, they attach with a 10-foot cable as HDMI and USB connections are required. Oculus now has a positional tracking sensor which works with the Rift headset. We've compared the Developer Kit 2 with the Samsung Gear VR
There are other PC-connected headsets, including the HTC Vive which was announced just weeks ago at MWC. This was designed in collaboration with Valve, the company behind the Steam gaming platform. See also: HTC Vive vs Samsung Gear VR
Using positional trackers placed on a wall and hand controllers, the Vive supports whole body movement and gives you haptic feedback, so you can reach out and really feel like you're picking up a physical object.
The other type of VR headset is a standalone device - or at least can be. Instead of using a PC, it takes advantage of a smartphone, using its screen and processing power to deliver the virtual world.
At its most basic, such headsets cost only a few pounds. Google Cardboard is widely available and is little more than a frame for holding a phone in front of your eyes. It incorporates a pair of lenses and a divider so each eye's image is kept separate. There's also a magnet which can act as a physical button for selecting options, since you can't touch the phone's screen. Here's how to make a Google Cardboard VR headset
Spend a bit more and you can get a higher-quality plastic VR headset with better optics, such as the Samsung Gear VR. It was developed in conjunction with Oculus, and is specifically for the Galaxy Note 4. However, at MWC a couple of weeks ago a new Gear VR - the Innovator Edition - was announced and the new Galaxy S6 and S6 Edge will fit.
See our Gear VR hands-on review
What makes a good VR headset?
As with any tech, VR headsets don't all give an equally good experience. The display is one of the most important aspects, but resolution isn't the only factor to consider. More pixels is better, but to avoid a nauseating feeling, the screen (and whole system) must not have motion blur and judder.
The screen technology, then is crucial, as is having very low latency. The current preference is for an OLED display, which is why Samsung's phone-based headsets should offer a decent experience.
Comfort, though, shouldn't be overlooked. A heavy headset, or one with lots of wires, is far from ideal. Portability should be lower on your list of priorities, but those with wall-mounted sensors will restrict you to one room.
Obviously price is a factor, but it looks very much as if you'll get what you pay for with VR headsets.
Content, arguably, should be the top priority. It's of little use having the best VR system if there are no games or other software for it. This is why it will undoubtedly pay to wait until well after all these VR headsets go on sale so you can make an informed choice.
Facebook bought Oculus in 2014, so there won't be a shortage of money behind the Rift. However, SteamVR could also be a formidable platform. We'll have to wait and see just how VR pans out.
Read next: All we know so far about PlayStation VR