Sorry, four of the power to ethernet plugs. You put one near your router to essentially supply internet to your house’s electrical circuits, then distribute the others where you need them, such as office, living room if you want to connect a TV or console, etc.
I was going to also post the direct AMA link, but the OP is a nice concise summary of many of the key discussions, provided without having to go to that site. I’d recommend reading that instead and follow links as you see fit.