Virtual reality often refers to the virtual environment or the technological interface where a user equipped with an head-mounted display can go to interact.

The purpose of virtual reality is to allow one person (or several) to have sensorimotor and cognitive activity in an artificial, digitally created world, which can be imaginary, symbolic or a simulation of certain aspects of the real world. [Fuchs, 1996], [CRTRV, 2004].

For example, the person in a virtual world is looking at a particular object, then he must have the feeling that he is actually looking at this object and he should also feel the sounds coming from this object and be able to have the sensation of manipulating this object.

Virtual reality also refers to a scientific and technical field exploiting computing (1) and behavioral interfaces (2) in order to simulate in a virtual world (3) the behavior of 3D entities, which are interacting in time between them and with one or more users in pseudo-natural immersion (5) via sensorimotor channels. [Fuchs, 1996], [CRTRV, 2004].