Squats are a great compound exercise. Simple variations in your stance can target your quads, hamstrings and glutes differently for more eye pleasing and complete muscular development. For example, the further apart your legs are the more you will work your glutes and the outer thigh sweep. If you keep your stance narrow - shoulder or hip width - you will then work the tear drop quad muscle more.
Additionally, if you keep the bar higher on your back you will have more direct focus on the quads than if you keep the bar lower similar in style to a powerlifter's stance. In those instances the weight will be more evenly distributed to your quads, glues and hamstrings. These muscles I have mentioned all work together during the exercise and that is why it is called a compound exercise. Vary your squat stance from workout to workout for a more complete polished look. You may not be as comfortable all the time since you will not develop a lifting groove as quickly but the benefits will far outweigh any negatives resulting in greater all around leg mass and muscularity.
