A reserve price is set by a seller who will not sell below a certain price. Bidders know there's a reserve price, but they do not know what it is. In order to win the auction, a bidder must meet or exceed the reserve price and have the highest bid. If no bidders meet the reserve price, neither the seller nor the high bidder are under any further obligation. You can't use reserve prices for Dutch Auctions.
Sellers start by listing a minimum price, or starting bid, and the number of items for sale.
Bidders specify both a bid price and the quantity they want to buy. All winning bidders pay the same price which is the lowest successful bid. If there are more buyers than items, the earliest successful bids get the goods. Higher bidders get the quantities they've asked for. Bidders can refuse partial quantities.