View source for Auction House FAQ Blizzcon 2011

===What’s the difference between the gold-based auction house and the currency-based auction house?===
The gold-based auction house uses in-game gold for purchases and sales. With the currency-based auction house, players will be able to conduct these transactions using actual currency from an authorized payment method or from funds that have been added to their Battle.net account. Players can choose to participate in whichever version of the auction house they prefer, on a per-transaction basis.