At least with the movie “The Matrix” in 1999  everybody knows what Virtual Reality, as briefly known as “VR”, is. In this Movie, humans live in a virtual world. This virtual world is controlled and designed by intelligent machines. But almost everybody means, that the world they live in it, is real.
The term “virtual reality” means in other words a “computer-simulated reality” In this virtual generated environment, a virtual world, the user can move and interact with the objects. The perspective and views changes with the movements of the user .
According to Mazuryk and Gervautz , Virtual Reality systems could be grouped in three different levels:
Level 1: “Desktop VR”: In this level, a virtual world is presented to the users on monitors, for example, in video games. It is the simplest type of Virtual Reality and almost everybody has already seen it.
Level 2: “Fish Tank VR”: This system is based on the desktop VR. In addition, the head movements of the user will be adapted to the displayed image (head tracking). This can be realized for example with a simple Webcam or Microsoft Kinect. This YouTube video demonstrates the differences between an image with and an image without head tracking.
Level 3: “Immersive Systems”: The user sees only the computer generated virtual world and can fully interact with it. So the perspective changes according to the users’ position or moves. In this case, more technical equipment, for example a Head Mounted Displays (HMD), are necessary.
A special point of virtual reality is the use of computer technology . Input and output devices are required for the representation of the virtual world or virtual objects. The easiest way to dive into a Virtual Reality world is to play video games with a console like a Xbox or a PlayStation. Today it is possible to use a state-of-the-art smart phone as a Head Mounted Display (HMD). Google currently offers so-called “Cardboards“. With one of these Cardboards and some appropriate apps, an Android or an iOS smart phones can be transformed easily into a HMD.
Probably one of the “most real” Virtual Reality system came from the fictional “Star Trek: Next Generation” movies . In this movies, there were rooms with a Virtual Reality system so-called “holodeck”. In an article in the New York Time , Nick Bilton wrote, that technology companies work on the realization of something like a holodeck. But it needs a lot of time and money, so a holodeck will not be available bevor 2024.
 M. Mihelj, D. Novak, S. Begus. (2014). Virtual Reality Technology and Applications. Springer:London
 T. Mazuryk, M. Gervautz Virtual Reality, History, Applications, Technology and Future. University of Technology, Austria: Wien
 R. Doerner, W. Broll, P. Grimm, B. Jung. (2013). Virtual und Augmented Reality (VR/AR). Springer: Berlin