How can I have a wired connection to more than one room?

Let's assume you have internet going into a junction box, and want your router in room 1, your Ethernet-connected TV  in room 2, another Ethernet-connected device in room 3, etc.. The simplest setup is to have something a router (e.g. an ASUS 68) at the junction box to be your main router, and to have wired connections to the other rooms. Alternatively, you can have a Google WiFi router connected to the junction box with a small switch (e.g. Netgear) to distribute wired connections to the other rooms.