In reserve-price auctions, the seller sets minimum prices that are not revealed to buyers. If there is no bid equal to a reserve price, the item does not sell. Of course, the buyer can always contact the seller after the auction is over and negotiate a new price if he or she really wants that pack of baseball cards. In an open-reserve auction, the starting price of the bidding is revealed. Usually, the highest bid for the lot wins.
Dutch auctions are really weird.
There are 100 bidders. Private auctions come in plain brown wrappers. Often used to sell adult items, bidders' e-mails aren't revealed nor is bidding displayed. When the auction is complete, only the seller and high bidder are notified. First you register by selecting a user name and a password, and providing your e-mail address.