The powerline adapters 'transport' the data signal along via your mains cables, i.e. you plug in one adapter into the mains and into your original modem/router, wherever it is positioned, and then you plug another one into a mains plug where you want the signal to be. You can then either access this via an ethernet cable between adapter and device, or you can connect a wifi router/transmitter to the adapter, and presto you have a wifi signal where you want it. Yiu could also use additional adapters if you need the signal boosted in several locations.
They really do work very well, are not expensive, and no cables involved at all.
We use them to get wifi into OH's studio, which is away from the house.