Monads are just monoids in the category of endofunctors

Can someone please explain what this means in 10 words or less? I don't have much time.

>>3
although in math categories are used to represent type hierarchies, and not just arbitrary graphs, like say neural networks or your video game map.

Think C/C++ class hierarchies, together with all the functions transitioning objects between said classes.

You can use the concept to reason about your video game world, but it is not that good for it, due to the dynamic nature of game objects, and their change during lifetime.