Points2shop works with different advertisers. They give points2shop their banners, and their links. Points2shop then has members who are interested in that offer that uses the offer. When that offer is used, points2shop gets paid for sending the customer to that website. When points2shop gets paid, we pay a big portion of that back to the member who completed the offer.
This makes for a happy relationship between everyone. The advertiser receives the members that they want, points2shop receives the funds to keep points2shop up and running, and then gives a portion of that money to the member.
Points2shop isn't a site that you get 'free' things from. Points2shop is a site that you earn things from. You are spending your time on the site, and receiving a gift in return.