* Motion is relative: There's no absolute motion. An object can be in motion relative to one frame of reference but at rest relative to another.

* Frames of reference provide a point of comparison: To describe motion, we need a point of comparison. The frame of reference acts as that point. It could be:

* The Earth's surface

* A train

* A moving car

* A stationary object

Example:

Imagine you're sitting on a train. Relative to the train, you are stationary. But, relative to the Earth, you are in motion.

In summary: To accurately describe motion, you must specify the frame of reference you're using. Without a frame of reference, the concept of motion becomes meaningless.