* When an object is moving: The frictional force acts in the opposite direction to the object's motion, trying to slow it down.

* When an object is at rest but a force is trying to move it: The frictional force acts in the opposite direction of the applied force, preventing the object from moving.

Let me illustrate with examples:

* Pushing a box across the floor: The frictional force acts backwards, opposing your forward push.

* A car braking: The frictional force between the brake pads and the rotors acts opposite to the car's forward motion, slowing it down.

* A book on a table: If you push the book gently, static friction will oppose your push, preventing it from moving.

Remember, friction always works to resist motion or the tendency of motion.