Shaders

Shaders have been changing and the Fixed-function pipeline has been removed since DX10 so you may want to keep current with which hardware you're programming for.

NVidia GPU Programming Guide

http://developer.download.nvidia.com/GPU_Programming_Guide/GPU_Programming_Guide_G80.pdf

Why use shaders?

https://developer.nvidia.com/sites/default/files/akamai/gamedev/docs/ShaderIntegration_China.pdf

Intro to shaders / an explanation of the pipeline changes

http://rbwhitaker.wikidot.com/intro-to-shaders

Shader Models vs Shader Profiles (Windows)

http://msdn.microsoft.com/en-us/library/windows/desktop/bb509626(v=vs.85).aspx

http://en.wikipedia.org/wiki/Shader

What is a shader you ask?