I don't think that is a fair comparison. Monad is a typeclass so it would be like explaining some specific Java Interface (and all the context for Interfaces) t

I don't think that is a fair comparison. Monad is a typeclass so it would be like explaining some specific Java Interface (and all the context for Interfaces) to a 5 year old. The Haskell (since you brought up Monads) equivalent to explaining Objects would be like explaining Records or Sum types, which would be very easy to explain and don't require talking about inheritance like Objects would.