In computer animation, joints refer to the flexible points or pivots that connect different parts of a 3D character's skeleton, allowing for movement and articulation. These joints act as rotational axes, enabling the animator to manipulate the character’s body parts like limbs, fingers, and facial features in a natural way. By setting up a hierarchy of joints, animators can control how parts of the body move in relation to each other, creating realistic motions and expressions. Proper joint placement and weight distribution are essential for achieving fluid and convincing animation in 3D models.