No Geek Needed Router?

My room is in the basement and my stepbrothers is in the attic, and we are three floors apart. In his room I get 1 bar wifi signal. Today he plugged in some "No Geek Needed Router" and he has full bars. The thing is there are no wires connecting to this router other than the router going to the wall for power, no internet wires. For this reason this thing does not work like a normal wifi router since you normally have to connect the router to a modem. How does this work? Is it just connecting to my signal and increasing its strength for him?