Follow through and overlapping action
When objects come to a standstill after being in motion, different parts will stop at different speed. Similarly, not everything on an object will move at the same speed. This forms the essence of the fifth
of Disney's principles of animation.
If your character is running across the scene, their arms and legs may be moving at a different speed from their head. This is an overlapping action.
Likewise, when they stop running, their hair will likely continue to move for a few frames before coming to rest – this is follow-through. These are essential principles to understand if you want your
animation to flow realistically.