What is a straight line a body rotates around?

A straight line that a body rotates around is known as the axis of rotation. This line can be internal, like the axis of a spinning top, or external, like the axis of the Earth as it rotates around the Sun. The rotation occurs in a circular motion around this axis, and all points on the body move in paths that are perpendicular to the axis. The axis can also determine the body's angular momentum and rotational dynamics.