Question about models

Inner structure of virtual bones connected to the skin (i.e outer surface) for proper animation...

ready for animation

Rigging is needed for animation or posing models. Non rigged models can only have transformational animation (move, rotate, scale), while rigged models can have both, transformational and deformational animations. For example rigged character, can be animated as walking, moving hands, talking, etc. Rigged vehicle, can have movable doors, trunks, wheels, etc.

For a character, per example, it means the character's articulations can be controlled by bones. Allowing for future animations.