The term “jaw” is referred to one or paired bones forming the framework of the oral cavity. Each human has two jaws - the upper and lower jaw. 

The upper jaw is formed by two paired maxillae fused with the sutures. It is not movable as the maxilla is a fixated part of the skull. 

The lower jaw is formed by an unpaired mandible. In contrast to the maxilla, the lower jaw is movable. The movements of the lower jaw happen at the temporomandibular joint formed by the temporal bone and mandible.

Both jaws contain teeth. And with the help of masticatory muscles, the lower jaw is moved. Therefore, all the mentioned structures are involved in digestion as they help to bite, chew, grind and hold digested food.