This is an easy-to-use and easy-to-install device which extends your existing Wi-Fi signal. Basically you set it up so that it gets signal from your router, and then you can place it somewhere at a distance from your router and connect a wireless device to the booster, for example; In the house 3 floor house I had at university we had our wireless router on the ground floor and this Wi-Fi extender on middle floor landing so we had better, stronger Wi-Fi on the top floor.
It's easy to set up - just plug it in somewhere near to your main router, and then hook it up to your computer via the included ethernet cable. You'll see the wireless signal with "Edimax" in the name, and connect to that. Then go to the website "http://Edimax.Setup" and follow directions. Once it's set up, you can place it anywhere you like, as long as it can pick up a signal from the original router.
What it doesn't do is boost the speed - in fact it slightly slows things down. It effect regular browsing, but it does effect activities including video streaming (TV catchup), so it's really a tradeoff in terms of getting a boosted signal farther away, but it's not as fast as it would be anywhere you could get a decent signal.
Overall this is a great product, as we had a far stronger signal on our top floor, and now I use it every now and again to get a better signal down my garden.