What are those levers for?
You might know what the overall effect of the throttle, prop, and mixture levers do, but do you know how your inputs really affect the engine? Do you know how a piston engine works?
Of course you don't need to understand these things to fly an aircraft. You can successfully go from one point to another without having to even think about that. But with more insight into how a piston engine aircraft works you can become much more aware of what your inputs with those levers are actually doing.
The purpose of it is to give a little more understanding of the power quadrant and how it works.