Auctions give you the opportunity to bid on a particular item. Each item on auction carries an allotted auction time. The highest bid at the end of the auction time will be rewarded the item.
Sweepstakes give you the opportunity to use reward points to purchase a chance to win a contest. Each entry will carry a point value. Submit that number of points for an entry.
CB Shop gives you the opportunity to use reward points to purchase an item. Reward points used for an item are deducted from your account in exchange for the item.