GLSL?  An Introduction

Florian Rudolf

http://nehe.gamedev.net/data/articles/article.asp?article=21

GLSL (GLslang) is a short term for the official OpenGL Shading Language. GLSL is a C/C++ similar high level programming language for several parts of the graphic card. With GLSL you can code (right up to) short programs, called shaders, which are executed on the GPU. This tutorial explains the difference between using the fixed function pipeline extensions and the programable pipeline of GLSL.