Please be gentle with me, I have very little knowledge of these things.
Our wifi doesn't reach my home office and son's bedroom upstairs, but the previous owner installed 2 ethernet wall sockets. So downstairs, I've got an ethernet cable from my modem in to the wall socket in the living room and I plug my laptop in to the other wall socket in the office and it works perfectly.
But in terms of getting wifi extended to the dead spots, would I need to get a mesh system like that's already been discussed in this thread, or is there something I can buy to plug in to the wall socket upstairs to extend my wifi?