Anabolic steroids - more properly termed anabolic-androgenic steroids - are synthetic derivatives of testosterone - the hormone that makes a man a man.
Testosterone has two different kinds of effects on the body: androgenic (development of male genitals, growth of body and facial hair, and deepening of voice) and anabolic (increased bone and muscle mass). While all steroids have androgenic and anabolic effects, some synthetic steroids have been developed with minimal androgenic effects.
Anabolic steroids work by helping the body's muscle cells produce more protein which, as long as the athletes works out, leads to increased muscle size and strength and, at the same time, also allows the body to produce more ATP, the "fuel" muscles need to move.
Oral versus injectable
Steroids are taken orally (pill) or through injection, usually in the upper outer quadrant of the buttocks. Some athletes, however, have been known to inject specific sites hoping to increase muscle size and/or strength in that area. Unfortunately, this strategy does not work and can damage the injection site.
Cycling and stacking
"Cycling" describes the use of steroids for certain specific time intervals: such as 12 weeks on, 6 weeks off, and then another 12 weeks on.
"Stacking" refers to the use of multiple steroids at one time. Many users will take a combination of oral and injectable steroid with the hope of enhancing their effects.
Scientists first isolated and chemically characterized anabolic steroids in the 1930's. During World War II, the Germans were rumored to have given their troops steroids to increase aggressiveness. In the 1950's, an American physician and weightlifter, John Zigler discovered that Russian weightlifters were using steroids. He developed a synthetic steroid, using himself as the guinea pig. When Zigler wrote about his discovery in popular bodybuilding magazines, the steroid craze began.