when you go to the auction house and put something up for sale, the people on your wifi list can see them and bid on them. just the same, if they put something up, you could see what they've put up and bid on it also. sadly though, not many people use this feature, because it doesn't work right if you time travel, and people just don't really see it necessary when we have the forums here with an auction house forum that's much quicker than having to wait like a week to put something up. and then it's only have it up for 2 days when people that may be interested may not even see it...
It's what it is; an auction house. Like the Auction House forum here at TBT. Except the in game auction house isn't being used to its full potential because nobody puts items up for bid there. <_<