Texture coordinates control the wrapping of texture on the surface of a model; these are 2D coordinates used to map texture on the 3D surface of the geometry. Texture coordinates are mapped to a different coordinate system called UV Mapping. Letters U and V denote the axis of the texture along the x and y axis, respectively:

The preceding extreme left image shows an icon that needs to be mapped to a blue-colored square of some arbitrary dimension. An image (irrespective of its dimensions) is always treated in the UV mapping between a range of 0 to 1 along the U and V axis, respectively. Therefore, the bottom-left image is always (0, 0) and the top-left image is (1, 1); there is no need to assign these values in the OpenGL ES program. By default, it's understood by the graphics pipeline.

What needs to be mentioned is the texture coordinates of the 2D/3D model; for example; in the previous image, the blue color square is assigned with four...