"Ball and socket," "hinge," "pivot" and "gliding" are all types of movable joints in the human body. A joint is a place where two bones meet and move in relation to one another.
A ball-and-socket joint such as that found in the hip or shoulder consists of the round head of one bone fitting into a cup-like structure on another bone. These types of joints give the most freedom of motion. Hinge joints are found in the knees and elbows, and they allow the bones to swing in only one direction. A pivot joint lies between the radius and ulna bones of the arm, allowing the end of the radius to rotate on the ulna. A gliding joint allows only limited motion and can be found between the bones of the wrist.