These sites conduct an estimated 2 billion dollars in business and are growing rapidly. Online auctions seem to work like a traditional auction with the highest bidder winning, from there, the methods change. The auction does not actually possess the item up for bid, they simply advertise the product. It is up to the seller of the product to arrange payment and delivery. The highest bidder is typically contacted via email with credit card payment option available.
Some sellers request payment by certified check or money order.
Be very cautious. Some online sellers have been known to put items up for auction, taken the highest bidder's money and never delivered the merchandise. Consumers paying by check or money order have very little recourse in getting their money back. If the merchandise is not forwarded to you upon payment, you can then challenge the charges with your credit card company. Verify the seller's identity.