Unknown 3D Maxter Question: Character Animations

I wonder how an animated characters works in games. Do they save many animation of a character to one file and make the engine to load them by ID numbers, or do they just make many animated bones and load them using same 3D characters? Or Is there any other way?

If anyone know the answer to this question, please post your answers clearly.


Thankyou in advance.

Check out bungies website - the guys who produced Halo, they describe how they do it.