Creatine is a naturally occuring nutrient found primarily in red meats and is stored mostly in the muscle cells of our body where it contributes to the generation of ATP, the primary energy source for muscle contraction.
Creatine supplements are the most researched of all sports supplements and have been demonstrated to improve strength, high intensity muscular stamina and increased muscle hydration and muscle cell volume. In short, Creatine helps you get bigger, stronger and faster.
As a standalone supplement, Creatine Monohydrate is a relatively inexpensive product, typically used at 1-5g per day for long term use. However there are a mass of supplements out there designed for fat loss, mass gaining and strength or power that all use Creatine as a base for the product.