Objects that change their position relative to their surroundings are said to be in motion. A car that is driving down the highway is an example of an object in motion.
Rest and motion are relative terms. What is considered to be rest in one frame of reference may be considered to be motion in another frame of reference. For example, consider a passenger sitting on a train that is moving at a constant speed. From the passenger's frame of reference, the train is at rest. However, from the frame of reference of a person standing on the ground, the train is in motion.
The laws of physics that govern the motion of objects are the same in all frames of reference. This is known as the principle of relativity.
