Texture mapping adds realism by attaching images to geometric surfaces.
Bump mapping adds per-pixel surface relief shading, increasing the apparent complexity of the surface. Surfaces that should have a patterned roughness are good candidates for bump mapping. Examples include oranges, strawberries, stucco, wood, etc. A bump map is an array of values that represent an object's height variations on a small scale. A custom renderer is used to map these height values into changes in the local surface normal.