Just about to move into a new build and this is in a cupboard by the front door...BT said simply plug in my router and it will work on the day they switch me over...NOT GOT A CLUE what to plug into what...there's no instructions anywhere...
https://www.bt.com/help/broadband/getting-set-up/how-to-set-up/bt-smart-hub-2/connection-modem
The plate on the right is an ethernet patch panel that will go to ethernet connections in other rooms. So after the router is up & running, you can connect ethernet cables between the router & the patch panel & then another ethernet cable to a device in the room. Or to an ethernet switch if you need more than one connection.
Of course until it's actually up & running you won't know what the WiFi coverage is like.