Virtual image is a term used in optics and physics. It is a representation of an actual object (source) formed by diverging rays of light which seem to originate from the image, but in reality do not cross at that position. A screen or an observer placed where a virtual image appears to be cannot actually "see" it.
For example, a plane or convex mirror forms a virtual image positioned behind the mirror. Although rays of light seem to come from behind the mirror, light from the source spreads and exists only in front of the mirror.
See also