Texture mapping is a graphic design process in which a two-dimensional surface, called a texture map, is “wrapped around” a three-dimensional object. Thus, the 3-D object acquires a surface texture similar to that of the 2-D surface.
In some mappings, the correspondence between the 2-D texture map and the 3-D object’s surface becomes “messy.” An example is the application of a pattern of squares to the surface of a sphere.
It is impossible to paste checkered wallpaper onto a sphere without cutting the paper in such a way as to create discontinuities in the pattern. This problem occurs with many texture mappings.

Texture mapping definition from WhatIs.com
Clement Valla