A ball joint is a ball joint. Ball head is a folk term. Ball joint is a scientific name. It is actually a "joint" device:
The simplest hinge is a tube placed on a shaft that can swing around it.
The structure of the ball head is actually very simple, with one end being a steel ball and the other end being a "ball bowl".
The "ball bowl" just wraps around the steel ball, and the steel ball can rotate freely inside the "ball bowl". The use of ball joints is very common in cars. For example, the pull rod of the steering wheel and the joint of the suspension arm are specific application examples of ball heads.