Here's why:

* Friction is a force that opposes motion. It arises when two surfaces rub against each other.

* Motion requires a force. To make something move, you need to apply a force to overcome friction.

Think about these examples:

* Walking: You push your feet against the ground (applying a force), and friction between your shoes and the ground allows you to move forward.

* A car braking: The brake pads rub against the rotors, creating friction that slows the car down.

* A sledding down a hill: Friction between the sled and the snow slows the sled down.

Without friction, things would slide and move endlessly! Imagine trying to walk on ice without any friction, or trying to stop a car with no brakes!

Key Points:

* Friction is a force that opposes motion.

* Motion requires a force.

* Friction and motion occur simultaneously.

Let me know if you have any other questions!