Follow Through and Overlap:
"When the main body of the character stops all other parts continue to catch up to the main mass of the character, such as arms, long hair, clothing, coat tails or a dress, floppy ears or a long tail (these follow the path of action). Nothing stops all at once. This is follow through. Overlapping action is when the character changes direction while his clothes or hair continues forward. The character is going in a new direction, to be followed, a number of frames later, by his clothes in the new direction. "DRAG," in animation, for example, would be when Goofy starts to run, but his head, ears, upper body, and clothes do not keep up with his legs. In features, this type of action is done more subtly. Example: When Snow White starts to dance, her dress does not begin to move with her immediately but catches up a few frames later. Long hair and animal tail will also be handled in the same manner. Timing becomes critical to the effectiveness of drag and the overlapping action." -Frank Thomas and Ollie Johnston. Because of weight and momentum objects down a chain begin and end a move at an offset starting from the root down. Think of the wagging tail of a happy dog. Video by Digital Tutors "Follow Through and Overlapping Animation". Check out Keith Lango's "Zen of Lead and Follow" as well as "offsetting keys vs. changing shapes."