ariel plug ??

Sorry if I have put this in the wrong section, my WiFi is shockingly slow, I have 1 x box set up on the ethernet and another box on WiFi, the second box buffers all the time, I have heard about some kind of a plug that can go into a normal household plug socket, you have one of these plugs on each box and it used the house earth to boost the signal. Has anybody used them, What are these plugs called
cheers