By just looking at the image, I think you will not get the whole idea about the function. You will have to download it to see working example. This is an explanation of how to animate different sections of a movie smoothly. When some button is clicked, the previous animation restores its original state or disappears in a smooth way and after that new movie appears or gains the new position.
For example we have two movies, lets say a and b.
these are at states 1.
When we click at button a for movie a, it animate in some way and goes to state 2.
When we click now at button b for movie b, then two actions are performed.
Firstly animation state of movie a which is 2, will be back to 1.
Secondly after first move, animation state of movie b which is 1, will be changed to 2.