Matching up the body

Ideally in the golf swing you want the body, club and arms to match up throughout the swing.  When this synching of body, club and arms match up you hit your straightest, most consistent shots.
When the body gets out of synch and moving faster than the club you'll have a tendency to leave the ball out to the right.  Likewise, when the arms and club move faster than the body, the club closes faster and the mistake will be a hook.
From a teaching perspective, you want to slow the body down and speed the club up to help fix a slice.  To fix a hook, the body needs to move faster and lead the club to impact.  These moves are as much timing of body parts as they are physical moves.