Creatine is a combination of amino acids. You get it in high protein foods like fish and meat, by supplementation or by producing it in your body after ingestion of the amino acids needed. Once it’s in your body (directly or by being made there) it will bind with a phosphate molecule and create Creatine Phosphate. When you’re doing a very intense, short duration exercise, your body begins getting its ATP from the Creatine Phosphate system. ~ Berceste