In this guide they explain what the BIOS is , what is does and they explain almost every setting you will find in a BIOS :
The BIOS is that dark, cavernous pathway to your computer's very soul that both beckons and repels the would-be performance seeker. The BIOS can open up major performance pleasure for you, or it can hide that one little pesky setting that's causing your daily bluescreen, and you just don't know why. If you royally jack your BIOS, you can toast your system to the point which you may need a system reinstall or some new hardware. Don't get me wrong--it's not as though it's all that easy to do major damage to your system via the BIOS. It's just a good idea to know what you're playing with and not change things around willy-nilly.