The squat is the cornerstone of any solid strength workout. It develops strength in the quads, glutes, lower back and abdominals. In fact, its been documented that squats activate over 200 muscles in the body.
When doing squats, always emphasize technique over weight lifted. 10 body weight squats are far more effective than 10 185 lb. squats done with poor technique. Instead of working the intended muscle, every rep performed with incorrect form actually makes us more likely to injure ourselves.
In the case of squats the injuries are typically to the low back and knees. Perfect it by focusing on hip movement, getting thighs parallel to the floor, keeping your weight to the rear of your foot (off toes) and not letting knees go beyond line of toes.