About shading models

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

ModelUseful for...Example
LambertMatte materials (chalk, matte paint, unpolished surfaces). 
PhongGlassy or glossy materials (plastic, glass, chrome). 
BlinnDull metallic materials (brass, aluminum). 
LightsourceA 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.