Difference between PreSale and Preview
PreSale is used primarily for selling tickets to an event (or any for sale items or appeals that are marked for presale). When your auction is in presale mode, your guests can only see items that have been specified as presale. If you have started adding your silent and live auction items, they will not be visible to bidders while your auction is in presale mode.
Preview mode is designed for your guests to be able to view your items and see what is available, but they are not able to bid on items in preview mode.