Seria a força necessária para mover as articulações do personagem.

http://forum.unity3d.com/threads/422-Switching-to-skeleton-t...

Yes. Hinges have a break force. You can modify it if you inspector is set to Full.

Well you have skinned a character in your 3D art program right?

Which means in your a 3D art program you have a bunch of bones.

When importing the character into unity, those bones get converted to Transform's where the Transform's have Animations attached.
So you don't add anything to the object with the mesh but only to the bones of your character.