what is rotation?
Answer
A rotation is a circular movement of an object around a centre of rotation. If three-dimensional objects like earth, moon and other planets always rotate around an imaginary line, it is called a rotation axis. If the axis passes through the body's centre of mass, the body is said to rotate upon itself or spin.

A rotation is a circular movement of an object around a center (or point) of rotation. ... A rotation around a completely external axis, e.g. the planet Earth around the Sun, is called revolving or orbiting, typically when it is produced by gravity, and the ends of the rotation axis can be called the orbital poles.​