[PaulAJ]

Monads are a unification of a bunch of computer stuff, including sequencing, IO, non-determinism, state, concurrency and exceptions. When I say "unification", I mean it in the sense that Newton's theory of gravity unified the motion of the planets with a falling apple (previously they were considered separate phenomena), or how Maxwell's equations unified electricity and magnetism. Once you grok monads you realise that all those different things I listed are just special cases of one overarching theory.