The simple version is that creatine helps load your muscles with water and that helps in recovery and to stave off the build up of lactic acid, which allows you to workout more.
No know side effects other than some intestinal issues and bathroom breaks.
Of course, like most supplements, its the quaility that is the issue.
T-Nation has many articles about it.
So does almost every other site on body building or strength training.
Psalms 144:1
Praise be my Lord my Rock,
He trains my hands for war, my fingers for battle !