"TMJ" stands for temporomandibular joint, or the jaw joint. The TMJs are the small joints in front of each ear that attach the lower jaw (mandible) to the skull. They allow you to perform such functions as opening and closing your mouth, chewing, speaking, and swallowing.
TMJ diseases and disorders refer to a set of conditions, manifested by pain in the area of the jaw and associated muscles and limitations in the ability to make the normal movements of speech, facial expression, eating, chewing, and swallowing. Conditions that routinely affect other joints in the body, such as arthritis and trauma, also affect the TM joint.