This is your third post since october 2002 and you're starting a thread on creatine. This made my day so much that I'm gonna answer your question.
Creatine monohydrate is absorbed from the gut and transported into cells, where creatine kinase borrows a phospate group from ATP. That is phosphocreatine. When ATP runs low, it will want the phospate back so the cell can keep using ATP as energy.
Any creatine will do, and creatine mono is the cheapest.