What is the mandible use in regard to the jaw?

The jawbone. is a bone forming the skull with the cranium (TMJ).
It forms the joint. The maxilla holds the upper teeth and provides occlusion for the lower teeth. It also forms the TMJ joint with the mandible.
Lower jaw. The mandible is the lower jaw, the maxilla is the upper jaw. These function against one another through the jaw joint - temporomandibular joint.