Power-line adapters are devices that turn a home's electrical wiring into network cables for a computer network. They come in handy when you need to bring the Internet connection to a far corner in the basement where Wi-Fi signals can't reach. A power-line connection is generally also more reliable than a wireless connection. With speeds up to 500Mbps, it's also faster.
To me it's a good choice to get connection reliability over the WiFi but not have the hassles to install the Ethernet cables.
Reference here provides a few good choices on powerline adapters.
