The squat is an exercise that works the legs and specifically targets quadriceps, glutes, and calves.

Execution: Begin by standing with the barbbell centered behind your head on your shoulders, holding it in place with your hands. Your feet should be spread in a comfortable, well balanced stance. Avoiding bending your back during the exercise. Lower yourself with the weight until your thighs are roughly parallel to the floor. Tense your legs, pushing down hard on the floor, to move the weight back up to the starting position. On the down motion your butt should stick out so that your thighs begin the descent and your knees will bend and accomodate.

Here are a few related entries that might interest you.

squat, Front Squat, Hang Clean, Calf Raise, ...