Here's why:

* Friction is a force that opposes the relative motion of two surfaces in contact. This opposition to motion means it acts to slow down or stop moving objects.

There are different types of friction:

* Static friction: The force that prevents an object from moving when at rest.

* Kinetic friction: The force that opposes the motion of an object that is already moving.

* Rolling friction: The force that opposes the motion of a rolling object.

While friction is often seen as a force that stops motion, it's important to remember that friction also allows us to do many things, such as walking, driving, and even holding a pen.