Overclocking is the technique of speeding up the CPU's FSB (Front Side Bus) to achieve a higher speed.
Example: Let's say I had an AMD Athlon 1.3 GHz CPU with a 133MHz FSB. Through the BIOS, I would change that Bus speed to 144. That in turn, yeilds a 1.4 GHz speed.

BE CAREFUL: Overclocking is not supported by most CPU and Motherboard manufactuers, and can permanantly damage your CPU and Motherboard. If you overclock to an extreme degree, be prepared to apply adequeate cooling as an increased frequency = hotter processor. Overclocking has also been rumored to shorten the life of your CPU as well...--SaiWolf 11:26, 22 Apr 2005 (UTC)