Materials indicate four basic properties of information about objects that are in the scene. They are: diffuse, emit, reflect and refract.
The diffuse channel is the most basic channel to apply to your object. It defines the colors that are going to bounce back from the surface to the camera.
The emit channel controls the illumination qualities of your object. This is a great channel to use when working with lightbulbs, little LED lights, etc.
The reflect property defines how much light/what kind of like is rejected by the surface back to the camera and the environment; creating highlights.
Refraction is the cousin of reflection. Unlike reflection, the refraction deals with how much light passes through the surface and then manipulates the position, color, shadows, etc. on the way out. the other side.