Parotitis is an infection of the parotid glands, which are located on either side of the face near the jaw. It is caused by a virus known as MUMPS, which is a contagious disease that can spread through saliva and respiratory secretions. Symptoms of parotitis include swelling and pain in the affected area, fever, headache, and fatigue. Treatment typically involves rest, fluids, and medications to reduce inflammation and pain. In severe cases, surgery may be necessary to remove the infected gland.