When folks ask "What is a monad?", they usually don't want the technical meaning, they're wondering what they can do to see why they should care or take the time to learn/use them. Here's a summary[0] that's as good as any I've seen.
> Summary. We have seen that a monad is a type constructor, a function called return, and a combinator function called bind or >>= . These three elements work together to encapsulate a strategy for combining computations to produce more complex computations.
[0] https://wiki.haskell.org/All_About_Monads#Summary