Textures are series of images used in computer graphics to associate locations on a visible surface with varying values. This association is typically done by mapping locations on the texture (usually two-dimensional, but other dimensions and types of textures exist) to locations on the rendered surface. Filtering is often used to smooth away aliasing when sampling values from the texture, usually involving multiple images within a texture called mipmaps.
In 3D graphics, the digital representation of the surface of an object. In addition to two-dimensional qualities, such as color and brightness, a texture is also encoded with three-dimensional properties, such as how transparent and reflective the object is. Once a texture has been defined, it can be wrapped around any 3-dimensional object. This is called texture mapping.
Well-defined textures are very important for rendering realistic 3-D images. However, they also require a lot of memory, so they're not used as often as they might be. This is one of the rationales for the development of the new graphics interface, AGP, which allows texture to be stored in main memory, which is more expansive than video memory. AGP also speeds up the transfer of large textures between memory, the CPU and the video adapter.