Many nutritional supplements make dubious claims, offering unproven benefits. A great number have proven to be ineffective or even unsafe. Creatine, however, is one of the most widely researched sports supplements and there are no serious safety concerns associated with its use, assuming that it is consumed in recommended dosages.
Creatine supplementation is typically divided into two phases: a loading phase and a maintenance phase. A typical loading phase comprises 20 grams of creatine (or 0.3 g/kg body weight) in divided doses four times a day for two to seven days. This is followed by a maintenance dose of 2 to 5 grams daily (or 0.03 g/kg body weight) for several weeks to months at a time (source: NSCA).
Creatine has proven to be very effective; research shows that it improves performance and increases lean body mass in males, females and the elderly, as long as strength training is performed concurrently and consistently. The increases in lean mass associated with creatine result from an increase in the protein content of muscle tissue.
Creatine is synthesized in the kidney, liver and pancreas, but is primarily obtained from the ingestion of meat or fish. However, strength and power athletes cannot eat enough meat or fish to supply their bodies with adequate creatine to improve performance. Hence, the need for supplementation. 
Marketed as “nature’s muscle builder,” creatine is an energy-boosting performance enhancer. Quite simply, creatine is a form of stored energy for muscles, primarily used by athletes and weight trainers.
Creatine helps provide energy to muscles during short-term, high-intensity exercise, making it ideal for strength and power athletes, rather than endurance athletes. Research shows that creatine supplementation during training can increase gains in 1-repetition maximum (1RM) strength and power.
One of the primary benefits of creatine is that creates a resistance to muscle fatigue. Muscle cells take longer to tire out when they have extra creatine in reserve. Creatine is an energy intermediate that helps replenish the fuel molecule adenosine triphosphate (ATP). Simply put, creatine can help you lift weights longer than you can without it.
In conclusion, creatine is safe, inexpensive and can increase your resistance to fatigue when weight training. It is the most legitimate sports supplement available.