Basically 2.6 is what most wifi devices run on, and 5 is like a secondary band you can use if 2.6 gets too crowded. Essentially what happens is your network gets bogged down the more devices being used on one frequency, so dual band is a method of trying to even out usage in a high wifi-use household. The downside is the connection drops much faster the further away you get because it's a higher frequency. I also have that router and it's pretty kick-ass on just the 2.6 band with my whole family using multiple devices at once. I think it would only really need to be used if there were, say, a party at your house, or extended family over. Otherwise, it's still a sweet heavy use router and extends throughout my entire decently-sized house.