The best way to get a definition of the term ‘Virtual Reality’ is to investigate both of these two words:
Virtual is originally a French word and means: apparently, the possibility to exist
Reality is an English word and means: Fact, Actuality
That means VR is a seeming, an apparent actuality. When we look for a definition that fits also for the informatic we can find one from Astheimer or from Dörner.
Astheimer says that “The term Virtual Reality means, that there are techniques which allow a person, to integrate directly into a computer-generated world. In this man-machine-interface more human senses are considered at the same time.”
Dörner says that“Virtual Reality (VR) describes the displacement of an observer to another, seeming reality using a computer system. Through special immersive VR technologies, the viewer should feel a presence in an apparent reality.”
To stimuli the human minds with the virtual sensations there are different interfaces:
Optical Interfaces: Interfaces for the visual perception system. These interfaces are the most important ones. There are different models like glasses or Head-Mounted-Displays.
Acoustic Devices: Devices which are to address the acoustic sense of the people are in an advanced development, but it is still complicated to implement the three-dimensional listening without the use of many speakers.
Possible UseCases for VR:
Car industry: Particularly in the development phase of a new car, the VR technologies plays a major role. If a new design of a car is developed, a three-dimensional computer-model of the car will be created that the design can be examined.
Medicine industry: In medicine, the VR technology is already in use for daily business. For example, organs are simulated virtually and serve as a training facility for young surgeons.
Entertainment industry: The greatest potential of VR is maybe in the entertainment industry. VR is increasingly used in cinemas, theaters, amusement park and the game industry. 
 A. Preisser, 2010
 Astheimer et. Al., 1994
 Dörner, 2009
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