Here's why:

* Motion is relative: There's no absolute frame of reference for motion. An object can be considered moving or stationary depending on what you compare it to.

* Reference point: This is a fixed or assumed stationary point or object that you use to judge the movement of another object.

* For example, if you're on a train and walk down the aisle, you're moving relative to the train's seats, but you're stationary relative to the train itself.

Examples:

* A car moving down the road: It's moving relative to the road, trees, and buildings.

* A plane flying in the air: It's moving relative to the ground and the air around it.

* A person walking on a moving sidewalk: They're moving relative to the sidewalk, but stationary relative to the ground.

Let me know if you'd like more examples or explanations!