There are several types of online virtual reality available, from interactive social environments to medical or physics simulations. When the environment is online, it provides the ability for several users to interact with each other simultaneously within the digital environment, regardless of their physical location. One of the most popular forms of online virtual reality is a social experience, sometimes taking the form of a structured game or a freeform world in which users are able to create and manipulate virtual objects. Simulations provide users with the ability to test theories, equations or other structures that would be difficult or dangerous to perform in the real world. The interface for online virtual reality worlds can be as simple as text commands from a keyboard and a monitor to a pair of special stereoscopic goggles and haptic harnesses.
By far, the most popular form of online virtual reality is a virtual social community. This can simply be a digital meeting place where customized avatars represent all the people in a current virtual location, or it can be an expansive virtual world where defined rules present challenges to the users, as is the case with a massively multiplayer online game (MMOG). The primary aspect that defines this type of virtual reality is the interaction between the users within the context of the world.
A social virtual reality environment can be based on a very realistic model of the world, allowing users to explore environments and locations that closely match real-world counterparts or are so completely fantastical or user-generated so that nearly anything is possible. The inclusion of a rules system, such as an MMOG in which each avatar has defined statistics and goals, can allow players to share the online experience with one another and make the virtual world appear more real. Some environments rely exclusively on social interaction as the main motivation for users to keep coming back to the virtual world, even creating an economy within the game that is tied to real-world money, giving actual monetary value to virtual objects.
There also are several medical uses for an online virtual reality setup. One allows collaboration between different hospitals around the world with a common virtual patient, or virtual representation of a drug compound that can be manipulated by the participants. Another application is used for children or other patients who cannot leave the confines of the hospital or who have limited mobility, allowing them to explore a virtual world and interact with others who are in similar situations.