It basically turns your computer into a WiFi hotspot, thus connecting your N3DS to your PC directly without using a router as a middleman. It does cost money ($10 iirc) if you want to change the SSID and want to avoid interruptions every half hour. Using a good router and dedicating it to streaming (meaning don't use the router you normally use for normal purposes) would probably give you similar results.
If you have a high end router, you don't really need to dedicate it to streaming, my 802.11ac ASUS RT-AC68U router gives great results even though I use it for everything.
