Hello. You have not shown the diagram to which this question refers, which makes it impossible for it to be answered accurately. However, I will try to help you in the best possible way.
The frictional force is present whenever two surfaces come into contact, they can favor or disadvantage the movement of these surfaces, one over the other and this movement that determines whether the friction should be more or less intense. When friction is in favor of movement, it is preferable that it be stronger. An example of this is the arito between our feet and the ground, allowing us to walk. When friction is opposite to the movement, it is important that it is less strong.