The most important characteristic of all moving bodies is that they change their position with time.
A body is said to be in motion, when it changes its position continuously with respect to a stationary object taken as the standard or reference point.
Note: So motion is not absolute, it is relative
For example a car is in front of the hut at A. But after 10 seconds, it has changed its position to B. Here, the hut is a reference point and the car is changing its position with respect to this stationary object. Hence the car is said to be in motion. In order to study motion in depth we must know the meaning of the following terms.