Virtual reality is a technology which allows the user to interact with a environment that exists only in a computer. Usually the word is reserved for immersive technologies such as HMDs (head-mounted displays) or small rooms whose walls are covered with screens, rather than simpler computer games such as World of Warcraft. The term was coined in the early 1980s, when computer technology was improving to the point of being able to create virtual worlds with at least a superficial sense of realness.
The concept of virtual reality has been popularized by dozens of books, movies, and TV shows, especially the 1999 movie The Matrix. The Matrix features a virtual reality so convincing that its inhabitants are unaware it is not the real world. In one of the movie's most famous scenes, the protagonist is "unplugged" from the Matrix and finds out he is merely one of billions of people living in special pods created by artificial intelligences. In the movie, rather than delivering the virtual reality experience through clumsy goggles or gloves, the sensory signals are sent directly to the user by way of a "brain jack," plugging into the user's occipital lobe. Although The Matrix is just a movie, numerous brain researchers have attempted to create devices similar to the brain jack, and it is only a matter of time until the technology becomes viable.
The potential benefits of virtual reality are numerous. In a futuristic virtual world, a pauper could live like a king, enjoying virtual riches and even virtual sex. More mundanely, interaction via virtual reality could allow businesspeople or friends to meet "face-to-face" even if separated by thousands of miles. Virtual reality has been suggested as a visualization tool. For instance, chemists could enter a virtual room filled with complex molecules, and perform "chemical tests" by manipulating these objects with their hands, just as someone might pick up a set of Legos® and play with them.