Follow Through & Overlapping Action

Follow through is the termination part of an action. Since actions do no really come to a sudden stop they slow down and follow through is exactly that(it slowly comes to a stop). Also, follow through is displayed if there are loose parts to the character or object and the weight of those loose parts dictates how slow/fast the speed will be. Overlapping actions means to start a second before the first action has completely finished. This is also supposed to make the animation more interesting.
Overlapping action sounds similar to follow through but what i get out of it is what connects follow through to make a stop.
These principles are presented when you are kicking a ball. When you kick the ball, you leg is still moving up and then you have to lower it down.

http://www.evl.uic.edu/ralph/508S99/follow.html