UV Mapping is a 3D modelling process of making a 2D map representing a 3D model. This map is associated with an image. In contrast to "X", "Y" and "Z", which are the coordinates for the original 3D object in the moddeling space, "U" and "V" are the coordinates of this transformed map of the surface. Then the image is backtransformed ("wrapped") onto the surface of the 3D object. For example, it is used to give an animated character a realistic looking face, but various other applications are possible.
external Image: LSCM Mapping with Blender