Rigging is a method of attaching bones or biped to a
'modeled character' or object in order to make them animate
or 'perform' actions. By attaching bones or biped the
'character' can walk,talk and make bodily movements.

Rigging is bone setup to create animation by any character.

Rigging is the process of bones setup to animate of an any 
object or any 3d charachter.we can link between bones or 
create relationship between bones that is rigging.