Creatine is a protein that is made naturally in the body from three amino acids (arginine, glycine and methionine).  Creatine combines with phosphorus to form phosphocreatine (PC) in your muscle cells.  This is an energy rich compound that fuels your muscles during high intensity activities.  Creatine supplementation enables you to sustain all out effort longer than usual and recover faster between sets.  Creatine also helps promote protein manufacture and muscle hypertrophy, increasing lean body mass  and reducing muscle acidity.  This allows more lactic acid to be produced before fatigue sets in and reduces muscle protein breakdown following exercise, resulting in greater strength and improved ability to do repeated sets.