A body is said to be in motion when its position changes with time with respect to an observer. The state of motion (or rest) not only depends on the body but also depends on the state of the observer. Note: Rest and motion are relative terms.

The length of path covered by a moving body between its initial and final positions is called the distance covered by the body. Distance is a scalar quantity, and its SI unit is meter. Distance always increases with time.

An arrow drawn from the initial position to the final position of a moving body represents the displacement. The shortest distance between the initial and the final positions of a moving body is the magnitude of displacement of a body. Note: Displacement is a vector quantity.