It is part of a large travel agency. There is Travelers Advantage, Military Advantage, Student Advantage, etc. They have negotiated airfare discounts (not military fares), rental car discounts, and hotel discounts. I used Travelers Advantage back in the mid to late 90's and was generally happy with them. However, airfares were a lot higher then and the discounts were 10% back then.
Now, I'm not sure that I would use them -- it's probably not worth all the hassle of mailing in receipts to get discounts, etc.