In strength training, the squat is an exercise that trains primarily the muscles of the thighs, hips and buttocks, hamstrings, as well as strengthening the bones, ligaments and insertion of the tendons throughout the lower body. Squats are considered a vital exercise for increasing the strength and size of the legs and buttocks. Although the squat has long been a basic element of weight training, it has in recent years been the subject of considerable controversy.
Some trainers allege that squats are associated with injuries to the lumbar spine and knees.[1] As a result, many trainers suggest that the standard olympic bar squat be modified in various ways, including the box squat and the Zercher squat. Others, however, continue to advocate the squat as one of the best exercises for building muscle and strength. Most old-school "Dinosaur Training" methods include the squat.
Squats are a competitive lift in powerlifting.
These facts were found at http://en.wikipedia.org/wiki/Squat_(exercise))