Same as other cashback sites, except that you get a percentage of what your friends and their friends earn. You get $5 bonus to start with that you can cash in after earning at least $5 (easily with the entertainment books that are now 50% off).
Cashbaq states they only pay you out once your refund exceeds $10 or more. Does the $5 count toward the bonus or do you have to get additional coupons ($5+) in order to get paid out? I doubt I would use cashbaq more than once.