Yes, that’s a diagram that you see, all will be explained in due time.
Two of my band directors once told me that a key to a great musical piece is changing dynamic levels. Dynamics in music refers to sound level and quality. No matter how nice a melody is, if it never changes or progresses it’s flat and can become a bore. The same can be said of a performance spectacle, whether in theater, choral singing, dance, and even performance modeling. 
