These TP-Link Powerline adaptors have been a godsend in our house, especially in the lounge where we've got a PC and internet TV. We have 4 now, dotted around the house.
Powerline adaptors are used for creating wired internet points anywhere in your house, where-ever there is a plug (so, technically, even in the back garden or garage if you have an extension built there). They work by plugging one adaptor in the mains near your modem/router and then plugging an Ethernet cable in, then plugging the other adaptor(s) in to various mains plugs around the house. The internet signal then travels through the electricity cables between the adaptors, giving you fast wired internet.
The new WPA4220KIT is the faster AV500 standard Powerline adaptor that can shift enough information around to make it suitable for HD TV streaming. I's incredibly easy to install (just plug both units in together, press a button and wait for the lights to turn solid, then you're ready to go) and works with all other current Powerline kits (not the old style homeplugs though that run at a much lower speed).
The added benefit of this kit is that it has a WIFI Extender, too, which can either boost your current signal using the same ID and Password or create a new ID to use elsewhere in the house. If your router has a WPS button all you need to do is press that and then press the WPS button on the Powerline adaptor you wish to use as an extender. The ID and Password will be automatically retrieved. After that, plug it in around the house somewhere and it will boost your WIFI signal.
If you have a BT Home Hub 3.0 then be aware that the WPS buttons are usually turned off by default as they've had security issues, but other routers should be fine.
Overall, an easy to install and fast piece of kit that I can highly recommend.