Material Operators, or MATs, are designed to use TOPs and GLSL programs (pixel and vertex shaders) to create materials for geometry.
The most commonly used MAT is the Phong MAT. The Phong MAT contains a large number of lighting options that allow the users to create some very unique lighting looks.
Depth MAT - can be used to get depth information from the geometry for a depth-pass render. It will not render any color.
GLSL MAT - a powerful material operator which applies Pixel and Vertex GLSL shaders to the geometry. Geometry can be deformed on the GPU using vertex shaders. Geometry must have Texture Coordinates and normals.
Phong MAT - applies a phong shader to the geometry. Geometry must have normals for specular shading to work. Geometry must have Texture Coordinates for any applied maps to work (ie Color Map, Bump Map, Specular Map, etc). Geometry can be deformed using the Deform parameter page. Phong MAT offer other advanced features for Transparency, Rim Lights, and Shadows.
Wireframe MAT - renders the wireframe structure of the geometry.