The Auction House is a HUGE part of MoW. This feature allows you player to player trading as well as selling something for a profit. As seen in the picture below this is where you would click to OPEN the Auction House, commonly known as AH.
In the AH as you can see in the picture below you can sell or buy various items, gears etc. You must place a bid price on the items you wish to sell, however you do not have to put a Buyout Price. At the end of the time limit the person who bids the highest will obtain the item while you obtain the vouchers they spend on it minus Snail's small tax fee of 10%. Unless you put up a Buyout price, then someone may buy the item without waiting out the full time. But again Snail will take it's tax of 10% out of the vouchers that the seller makes.