Graphs are mathematical models. They are a very useful way of describing relationships. Graphs are especially useful when describing the motion of the objects, that is, any moving object changes is position with respect to time.
Normal Force- is the support force exerted upon an object that is in contact with another stable object. The book and the table are both exerting forces but since they are stable none of them will move.
Coefficient of Friction is the ratio between a force being moved horizontally and a force being pushed down. I chose this picture because it shows the force going horizontally and it shows a force pushing down it also tells the ratio of the multiple forces that are acting on the box.