[knubie]

If you understand promises you pretty much understand monads already since promises are more or less a type of monad.

Monads represent computation contexts. In the case of promises, the computation is preformed in the context of a value that will be available some time in the future (or not at all in some cases).

   my_promise.then(compute_result)

Another context could be a list, where the computation is performed on each value in the list

    my_list.then(increment)

Or the context could be that the value is maybe null

    maybe_string.then(uppercase)

How the computation is actually performed depends entirely on the monad. Usually .then is called .bind or .flat_map because it will automatically unwrap nested monads.