Not an explanation, but they key thing to know is that monad is not a thing, but a pattern. It's a pattern for composing things. Like the FP equivalent of the Unix shell pipe character. Like the Unix shell provides composability for processes that happen to read from stdin and write to stdout, most FP languages provide a framework for composing monads (of whatever kind) neatly e.g. Scala and Haskell "for comprehensions".