From Aeria Browser Wiki
Monitors buying and selling goods and offers services by offering them up for bid, taking bids, and then selling them to the highest bidder. Use everything you learnt from Business School here! Auction House is accessed in the Market at the NPC Colette.
Auction House allows player can engage in trade with others. To start an auction, you need to place an item in the auction tab for sale, set the minimum bid price and buyout price, then choose auction time. A certain amount of coins will be deducted as item storage cost. The quantity deducted is dependent on the length of auction time and the quality of the item being put up for sale. Items are sold for Gems. When a trade is successful, the Sire will receive an in-game mail detailing how many gems the item sold for and how many gems were deducted as a tax for the final price. Sires will also receive a mail each time the item is bid upon. If a trade is not completed within the time frame, the item will return to the Sire in mail. Auctions can be canceled by the Sire at any time. The coins spent to put the item up for auction will not be returned.
Up to 10 Items can be put up for sale at a time. Items are put up for sale under the Auction Tab. Items that have been bid upon can be watched in the Active Tab.
--Vampofval21 15:59, 29 August 2012 (EDT)
Auction House in ddtank however is different, for instance no limit to how many items you can have up for sell.