Parallax Mapping

Similar to parallax scrolling, parallax mapping creates the illusion of depth in a texture, by doing this it's possible to achieve greater realism with little influence on the game performance.  Parallax mapping is commonly used in stone or brick textures. It works by colouring an image of something such as bricks, in a way that from a distance, gives the illusion of depth and shadows. The use of these fake shadows and lighting causes the flat image of rocks to appear to be casting self-shadows and therefore have depth even though it is a 2D image.
  
It appears in Gears of War, Oblivion, Fear, Bioshock, Crysis, Fallout 3, Perfect Dark Zero and Kameo, to name a few.