Lateral inversion is the visual illusion that left and right sides of a mirror image are switched. A person looking in a flat plane mirror who raises his right hand sees his mirror image's left-side hand raise.
Lateral inversion is an illusion because, in a plane mirror, the image inverts on an axis perpendicular to the surface of the plane. This means that the mirror image, also known as a virtual image, is the front-to-back invert of the object. Two plane mirrors that are placed at a 90-degree angle from each other create a non-reversing mirror image in each other.