These plugs are superb, what you'd expect from a German manufacturer.
If you want internet connectivity around the house, upstairs and downstairs, and can't rely on wifi throughout the house due to distance or thick walls or have equipment that is not wifi ready...these are the answer.
They simply carry the internet connection through the mains power wiring of your house meaning internet connectivity is available anywhere there is a conventional mains plug.
My wifi router connects wirelessly to my laptop and PS3 which is great. However I have an internet enabled TV and an old PC upstairs which are not wifi enabled so these plugs put these on the web without trailing wires around the house. I'll tell you how...
The first homeplug is plugged into a conventional three pin mains wall socket in the lounge and the router connected to the homeplug via the supplied network cable. Then another homeplug is plugged into a mains socket upstairs and connected to my ageing desktop pc (that is not wifi enabled) with the supplied network cable, voila, the pc upstairs is on the internet without trailing wires! I have a third homeplug that is plugged in behind the tv which attaches the tv to the internet for Lovefilm streaming without trailing wires from the router!
I have a pair of white homeplugs too, I think the SE just refers to them being black.