Virtual reality (VR) is a name given to computer-generated stimulation of the senses in a manner closely approaching reality. VR is most effective when a person is able to interact with a virtual environment via some form of human-to-computer interface. In most cases, the interface stimulates the visual and/or auditory senses via computer monitors and headphones or loudspeakers. Flight simulators, in which pilots are trained to fly modern aircraft without leaving the ground, are examples of a virtual reality environment that provides appropriate sensory stimulation and reacts to inputs from pilots.

These articles are restricted to the most basic form of virtual reality, the use of spherical panoramas to immerse a viewer in a virtual visual environment, so only the stimulation of the visual sense is considered. However it does not require a huge leap of imagination to realize that basic auditory stimulation could be added with relative ease.

The basic process is relatively simple in principle. It involves creating a visual representation of a viewer's environment by photographing what he or she might see from a particular location when the head and eyes are turned in any direction. A number of individual images are stitched seamlessly together to produce a panorama extending over the entire surface of a sphere, as illustrated in the diagram on the right. The user is then effectively placed at the centre of the sphere and is able to move the spherical image around its centre by simple commands input on a computer. Ideally, these commands would be generated by the movement of the user's head and eyes, but these articles are concerned only with the creation of the spherical panoramic image which, in a basic implementation, is rotated or moved by dragging the on-screen image with a computer mouse.

The experience of the viewer, particularly when the panorama is viewed full-screen on a large monitor in high definition, is comparable with that of standing in the centre of a bubble on the inner surface of which is projected a continuous image of the environment - from the sky overhead to the ground on which the viewer stands. This is truly immersive photography.