Mike Malaska reviews the ball position series. There is an ideal setup and ball position for your different clubs.
Starting with wedges, most of your weight is on your left foot. The ball position is in the center of your body, and you are up on your left side. This means your swing will bottom out just in front of the ball, and you will swing steeper into the ball.
With the fairway woods and rescues, the ball is more forward, and additional weight is on your right foot. It changes your angle of approach, where you still hit the ball and brush the ground in front.
When using your driver, the ball is the most forward and is off your left heel with a little more weight on your right foot. Your swing bottoms out behind the ball, and you catch the ball slightly on the upswing. Because the ball is up on a tee, it is one of the few shots that hitting up on the ball is optimal. The putter is the only other club that works the same way.
Ball position and setup help the circle of your swing to accommodate what you are trying to do with the club.