http://www.youtube.com/watch?v=ryVNG6WPCxg
The synchronising stage is the culmination of what has gone on throughout the entire process. Matching the sound to the animation, this is part of the editing process. Not only does it include ensuring that spoken word is matched perfectly to the lip synch animations, it also means that music kicks in at the perfect time. For example dark, angry music might come on when a villan enters the room however if it comes in too early or too late, it can give completely the wrong impression. Below is a good example of how poor dubbing, sound acting ... and animation, can make a video look amateurish.
That's it, the sound production is now finished and can be added to the animation to make the final piece.