Here's what that means:

* Frame of reference: Imagine a coordinate system, like a grid, where you define your position and movement.

* Relative: Your motion depends on the frame of reference you choose.

Examples:

* Standing still: You might think you're not moving, but you're actually moving at a very high speed relative to the sun (because Earth orbits the sun).

* Walking on a train: You're moving relative to the train, but not relative to someone else also walking on the train.

* Driving a car: You're moving relative to the ground, but not relative to the driver next to you.

Key takeaway: Motion is not absolute. To describe it accurately, you need to specify your frame of reference.