Powerline networking explained
If you’ve just got one room where the Wi–Fi is a bit unreliable, then you can use a pair of inexpensive PowerLine adaptors to magically send your internet connection over your home’s existing electrical wiring.
One adaptor is plugged into a wall socket that’s close to your router, and connected to the router with an Ethernet cable.
Another adaptor is plugged into a wall socket in the room with the weak Wi–Fi signal, and the two adaptors can then connect together over the electrical wiring. Then you just plug your Mac or other devices into an Ethernet port on the PowerLine adaptor and you’ve got a fast, reliable internet connection in no time at all.