Dual band routers are exactly that, routers that support both bands (5Ghz and 2.4Ghz). The benefit of this is to split and share data between the 2 wireless frequencies making for faster transfer rates. You may also avoid microwave and 2.4Ghz interference 802.11a runs at 5Ghz. 802.11b Runs at 2.4Ghz, 802.11G Runs at 2.4Ghz, 802.11n supports 2.4Ghz and 5Ghz.