Auction - Bidding on an auction is done in specified increments. The user with the highest sucessfull bid "wins" the auction and the ability to purchase the item. Auctions use Proxy Bidding (see definition below).
Fixed Price Item - All Fixed Price items are Buy Now, hence bidding does not apply
Proxy Bidding - An automatic method of bidding that increases your bid to the next lowest price when another user bids on the same item. Your bid is increased until your maximum bid amount is reached or the auction ends.
