I just don't understand how it works. Like, if I wanted to run a service, would I run a Docker container for the database, webserver and backend, or would I run them all in the same container? How does one container talk to another? What if I wanted to run a reverse proxy? Would I use a container for that, or just run that on the host OS itself and just proxy pass all the traffic to the necessary ports? What if I wanted to scale?