A bluffer's guide to shaders
 

we have an article up which aims to de-mystify shaders. We look at the evolution of graphics hardware from the first T+L GeForce to the current shader model 3 hardware. We also look at what shaders actually are, and what the different shader model revisions actually mean to gamers and hardware enthusiasts. If you're puzzled by pixels or vexed by vertices, this guide should help you out.

Link
http://www.bit-tech.net/hardware/200...shaders/1.html

"Shaders are small programmes that alter pixels or vertices. Consequently, there are two major types of shader - pixel shaders and vertex shaders. These programmes add effects to basic geometry - so a water-styled shader can be added to a flat blue texture to make it look reflective, or a glass-styled shader can be added to a polygon to make it appear transparent."

"There are added complications - for example, the GeForce FX architecture, whilst Shader Model 2.0 compliant, allowed for a little bit more on top - allowing developers to code (almost) proprietory code where it was needed to compensate for the performance that the FX lacked in hardware. ATI have been heavily stood by the 2.0b shader standard, which has meant that games developers have had to code for 1.1, 1.4, 2.0b and 3.0 to fully support the range of hardware on the market."