Here's a breakdown:

* Friction is a force that resists the relative motion of any two surfaces in contact. It always acts in the opposite direction of the motion.

There are different types of friction:

* Static friction: This force prevents an object from moving when a force is applied to it. For example, the friction between a book on a table and the table itself.

* Kinetic friction: This force acts on an object that is already moving, slowing it down. For example, the friction between a car's tires and the road.

Other forces can also oppose motion in specific situations, but friction is the primary force that resists all motion.