http://en.wikipedia.org/wiki/Creatine
Creatine as a supplement will increase the amount of fluid your muscles store, causing a bulkier look and feel. It also increases the amount of energy you have. Creatine is naturally created in the body to be used in the chemical process of forming ATP, energy. A supplement of creatine simple add more fuel for energy.
As for definition, creatine will not necessarily help with this. You may want to supplement with it to add muscle, then cycle off and perform a workout routine that concentrates on toning. (Build bigger muscles, then tone up, leads to greater definition.) Be sure to drink plenty of water with the creatine and avoid caffeine. Caffeine dilutes the creatine and inhibits the absorption into the body, thus you simply urinate it all out.
You should have little difficulty buying a 99% to 100% pure creatine from either a health food store or even your local mega store. I personally would take creatine starting in week 2 and then cycle until the end of week 5. As I said in an earlier blog post -- be sure to drink lots of water. It is also not recommended to mix your pure creatine in any acidic beverages such as orange juice.
