Creatine raises your ATP levels, which can allow you to do a few extra reps per set. Creatine doesn't really build muscle, it allows you to train harder, which helps your muscles grow. Also I've read several articles that states, creatine can help you absorb more protein, I'm not sure if that one is true. Water retention is a side effect of creatine use, it will subside when you clear the creatine out of your system, it usually takes a few days to a week for me to lose the bloating.