Here's why:

* Friction is a force that opposes motion between two surfaces in contact. It always acts in the direction opposite to the intended motion.

* Applied force is the force that is directly applied to an object to cause it to move or change its motion.

Let's take an example:

Imagine pushing a heavy box across a floor.

* Friction acts against the box, trying to keep it stationary.

* You apply force in the opposite direction of the friction, overcoming it and causing the box to move.

Other relevant concepts:

* Normal force: This is the force that the surface exerts on the object perpendicular to the surface. It is important in determining the magnitude of friction.

* Net force: The sum of all forces acting on an object. If the applied force is greater than the frictional force, the net force will be in the direction of the applied force, causing the object to accelerate.

Let me know if you'd like more detail on any of these concepts!