In ‘second item’ bidding, a seller offers more than one identical item for sale per lot. This means that it’s possible for there to be more than one winner of a lot. Bidders must publicly indicate the price they are willing to pay for each item. To compete with other bidders, participants must bid a higher amount per item than the competition, regardless of the quantity of items that are being bid for.
If there happens to be more successful bids than there are items available, priority goes to those bidders who submitted their bids first. All winning bidders are obliged to pay no more than the lowest successful bid. This type of auction is sometimes confused with Dutch auctions and Vickrey auctions.