Imagine dragging a cat that is asleep. The cat is asleep and you are dragging it across the floor. In physics, you will learn that the friction force depends on two things: the weight of the cat and the atomic roughness of the floor.

Now, imagine that same cat planting its feet and using its muscles to resist your motion. The frictional force has NOT changed, because the weight of the cat is the same and the floor is the same. Nevertheless, the cat is now much harder to move. The difference is that the cat is now also applying a force with its muscles to resist the motion.

Think about tug-of-war. If we could not resist a pull with anything more than the frictional force, then the strength of the people on the tug-of-war team would not make a difference: the heaviest team would win, because they have the most friction. However, that’s not the case: the strongest team wins, because they can apply the greatest force with their muscles.