Well, that diagram at the end is something I've been looking for, for the longest time. I haven't been able to find a concise relationship of all the functional

Well, that diagram at the end is something I've been looking for, for the longest time. I haven't been able to find a concise relationship of all the functional terms/interfaces. I think the part that eludes many tutorials and articles, is explaining what exactly we're calling a monoid or a monad. Is it the actual set of laws? Is it an abstract "object"? And although there are many attempts at simplifying their explanations, I found that is necessary to grasp the concept of a category first. Really having an intuition for a category gives way to understanding functors, etc. because that's what their definition is based on. Attempting to explain functors, etc. just with functions (of any language) will leave the learner hanging as to what exactly a functor is, since languages just implement them, but category theory provides the underlying abstraction that gives them context.