I have never, ever seen "Monads are just monoids in the category of endofunctors" used in an actual conversation with someone who is trying to learn monads. The phrase is and always has been a joke; surely part of the joke is that most of us who use monads don't understand all that jargon ourselves. http://stackoverflow.com/questions/3870088/a-monad-is-just-a...

BTW, the article asks about design patterns that structure functional programs. Well, monads are one such pattern. That's why they're important, not some mathematical jargon.