Simple? Maybe, it's a complicated thing. A computer chip is designed to
run at a certain speed. Of course, most can run much faster than the rated
speed...The clock sets the speed of the chip, if you over clock, it will run
faster and you have a faster machine. The trade off is, the faster it goes,
the hotter it gets. If you do overclock, you also have to keep the chip
cool.
Look here for more on the subject, although not simple...
http://en.wikipedia.org/wiki/Overclocking
