What does arranging figures in a pyramid shape indicate?

Basically, when we say pyramid, this is polyhedron which is similar to the shape of a triangle. It has a broad base and a common vertex. When figures are arranged in a pyramid shape, this shows that these figures indicate an increase and progressive changes or transformation. Commonly, the one that is found below (base) is the foundation or origin, and as it increases, the origin undergoes a series of transformation making it better than it was. A good example of this is the energy pyramid. This shows the origin of the energy (base) and shows how the energy is being transformed as it increases in the pyramid. 

Answer(a)   the matererials that are in contact, the two materials and the nature of their surfaces/// (b)/// the force pushing the two surfaces together, pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other