Virtual reality (VR) is a technology which allows a user to intereact with a computer-simulated environment. Most virtual reality environments are primarily visual experiences, displayed either on a computer screen or through special stereoscopic displays, but some simulations include additional sensory information, such as sound through speakers or headphones. Some advanced and experimental systems have included limited tactile information, known as force feedback.

Users can interact with a virtual environment either through the use of standard input devices such as a keyboard and mouse, or through multimodal devices such as a wired glove, the Polhemus boom arm, and/or omnidirectional treadmill.

The simulated environment can be similar to the real world, for example, simulations for pilot or combat training, or it can differ significantly from reality, as in VR games.

In practice, it is currently very difficult to create a high-fidelity virtual reality experience, due largely to technical limitations on processing power, image resolution and communication bandwidth. However, those limitations are expected to eventually be overcome as processor, imaging and data communication technologies become more powerful and cost-effective over time.

The origin of the term virtual reality is uncertain though it has been credited to The Judas Mandala, a 1982 novel by Damien Broderick where the context of use is somewhat different from that defined above. A related term coined by Myron Krueger, "artificial reality", has been in use since the 1970s. The concept of virtual reality was popularized in mass media by movies as 'The Lawnmower Man' (and others mentioned below), and the VR research boom of the 1990s was motivated in part by the non-fiction book Virtual Reality by Howard Rheingold. The book served to demystify the heretofore niche area, making it more accessible to less technical researchers and enthusiasts, with an impact similar to what his book The Virtual Community had on virtual community research lines closely related to VR.

While virtual reality originally denoted a fully immersive tethered system, the term has since been used to describe systems lacking wired gloves, full body touch suits, etc., such as those driven by VRML and X3D on the World Wide Web and occasionally even text-based interactive systems such as MOOs or MUDs. Non-immersive virtual reality uses a normal monitor, and the person manipulates the virtual environment using a keyboard, a mouse, a joystick or a similar input device. The term was used in the early 1990s to denote 3D computer and video games, particularly first-person shooters.

Morton Heilig wrote in the 1950s of an "Experience Theater" that could encompass all the senses in an effective manner, thus drawing the viewer into the onscreen activity. He built a prototype of his vision dubbed the Sensorama in 1962, along with five short films to be displayed in it while engaging multiple senses (sight, sound, smell, and touch).

Predating digital computing, the Sensorama was a mechanical device, which reportedly still functions today. In 1968, Ivan Sutherland, with the help of his student Bob Sproull, created what is widely considered to be the first Virtual Reality and Augmented Reality (AR) Head Mounted Display (HMD) system. It was primitive both in terms of user interface and realism, and the HMD to be worn by the user was so heavy it had to be suspended from the ceiling, and the graphics comprising the virtual environment were simple wireframe rooms. The formidable appearance of the device inspired its name, The Sword of Damocles.

Also notable among the earlier hypermedia and virtual reality systems was the Aspen Movie Map, which was created at MIT in 1977. The program was a crude virtual simulation of Aspen, Colorado in which users could wander the streets in one of three modes: summer, winter, and polygons. The first two were based on photographs - the researchers actually photographed every possible movement through the city's street grid in both seasons - and the third was a basic 3-D model of the city. In the late 1980s the term "virtual reality" was popularized by Jaron Lanier, one of the modern pioneers of the field. Lanier had founded the company VPL Research (from "Virtual Programming Languages") in 1985, which developed and built some of the seminal "goggles n' gloves" systems of that decade.

It is unclear exactly where the future of virtual reality is headed. In the short run, the graphics displayed in the HMD will soon reach a point of near realism. The aural aspect will move into a new realm of three dimensional sound. This refers to the addition of sound channels both above and below the individual. The virtual reality application of this future technology will most likely be in the form of over ear headphones.

With our technological limits today, sight and sound are the only two senses that will be able to be replicated almost flawlessly. In order to engage the other senses of touch, smell, and taste, the brain must be manipulated directly. This would move virtual reality into the realm of a vivid dream not dissimilar to "The Matrix". Although no form of this has been seriously developed at this point, Sony has taken the first step.

On April 7th, 2005 Sony went public with the information that they had filed for and received a patent for the idea of the non-invasive beaming of different frequencies and patterns of ultrasonic waves directly into the brain to recreate all five senses Times Online. There has been research to show that this is possible. Sony has not conducted any tests as of yet and says that it is still only an idea. Continued