. . . you're the only bidder. If a seller wants $100 for an item and puts a $100 opening bid, you can bid and get it. If a seller wants $100 and puts a reserve on it, your bid starts at whatever they set at the opening amount but never goes up if another bidder doesn't enter the fray. Even if you were willing to pay more, your bid stays at the opening bid amount because no one else was interested or the rest of us didn't want to play around with a reserve auction