Listen Server

I’ve been looking for explanation on what ListenServer means in Unreal and it left me confused.

Does Listen Server means - a client that also behaves as a server (and it would return “Authority” and not “Remote” when checking “Switch has authority”)? Or is it a client and server both running on the same machine, each with it’s own game instance where client is “Remote” and server is “Authority”?

So basically, If I play a multiplayer game with “Number Of Players” property set to 2, and I connect to Listen Server, does my “opponent” runs server code or client code as well?