Under The Stairs
From MythTV Official Wiki
Under the Stairs is a jargon name for a separate backend machine that sits out of sight and rarely needs to be touched.
You can run multiple frontends from a backend, or have a single master backend and additional slave backends to help with the load of Commercial flagging, or simply to run additional tuners.
Another way to interact with the remote backend is MythWeb, which allows any OS to schedule recordings via a web page interface.