With proxy bids, you set the maximum amount you think you want to pay for an item. You authorize (or give your proxy to) the auction system to increase your bid on your behalf up to the amount you designated. The Auction Site will automatically keep you in the lead (upping your bids by the minimum bid increments) until hitting the maximum amount you specified.
Example:An item is at $300 and you set a limit bid of $500. Each time someone adds a bid, your bid will automatically kick up to the next increment, rendering you top bidder.
Tip: Always check your watch list to see if someone has bid beyond your maximum.