We bought this for my son when he moved into rented accommodation to create a secure WiFi hotspot as his room was at the back of the building quite a way from the router. We had to plug the device into an electric socket close to the router and then connect that to the router with the cable supplied. We then plugged the additional plug into an electric socket in his room which creates the hotspot. We especially liked that it was secure meaning he could access sites without passwords and other info being compromised. The signal was strong enough for online gaming and watching Netflix.
You could also connect with a cable instead. This was a more sightly option than running lots of long cabling from one room to the next.
Product link: http://www.amazon.co.uk/gp/product/B00ECBRGW8