To this point we've only used textures as labels over geometry.
Their applications are much broader, however.

Simple extensions include:

• Spatially varying surface properties:
  • The diffuse shading coefficient, k_d, could be stored as a texture.
  • Likewise for the intrinsic color, k_a, k_s, and n_shiney.
• Textures can also be used in a lot of other ways

Many of the following slides and images are provided by Justin Legakis.