Major settings for the shader can be altered here.
The name of the shader, as shown when selecting a shader in the material panel.
The Diffuse defines one part of how the shader interacts with light, along with the Specular.
The Specular defines the shiny parts of the shader, and creates how it interacts with light along with the Diffuse.
The Emission allows parts of the shader to glow, even when there's no light.
The Transparency settings allow you to set if see-through parts are allowed, and how they work.
Shells are copies of the model that grow outward, and can, for example, be used for grass or cartoon outlines.
POM (Parallax Occlusion Mapping):
POM allows you to create fake displacement using an advanced shading technique.
Tessellation lets you increase the polygon count within the GPU, allowing additional surface detail like individual bricks or strands of fur.
Miscellaneous settings are settings that didn't really fit anywhere else.