If the position of an object does not changes with respect to other objects in its surroundings, it is said to be at rest. If the position of the object changes with respect to other objects in its surroundings,it is said to be in motion.
An object is said to be in motion if it changes its position with respect to its surroundings.
An object is said to be rest if it does not change its position with respect to its surrounding.
Rest and motion are relative terms because at a sometime a body can be in rest with respect to one body and can be in a motion with respect to another body .e.g passenger sitting in a bus is in a rest with respect to another person sitting in a bus but the same person is in motion with respect to outside surrounding.
When a body is moving in a circular path after making one complete displacement is zero but distance isn’t zero.