A shading model is a representation of how light bounces when it hits a surface. Different models simulate different types of materials better.

Model	Useful for...	Example
Lambert	Matte materials (chalk, matte paint, unpolished surfaces).
Phong	Glassy or glossy materials (plastic, glass, chrome).
Blinn	Dull metallic materials (brass, aluminum).
Lightsource	A special lighting model that has no shading. Can be used to represent, for example, the surface of a switched-on lightbulb. Objects shaded with this model do not cast light into the scene.

These shading models and their parameters (for example, color, shininess, and reflectivity) determine the base look for a shader. You can then modify the base look by mapping different types of textures onto the shader parameters.