Rest and motion are relative terms.
Rest and motion
In simplified way, an object in motion is one that changes its location, while an object at rest is one that does not change the location.
Motion – An object is said to be in motion if the position changes with respect to it surrounding and time.
Rest – An object is said to be at rest if it does not change its position with respect to its surroundings with time.
Rest and motion are the relative words since because they are based on the observer’s frame of reference. If an observer is stationary in their own frame of reference, they may be travelling in the frame of reference of another observer. So, if two observers are not at rest in relation to each other, they will observe the motion or rest of a body and come up with different results.