How it works is you sign-up and complete 1, only 1, offer. Many, if not most, of the offers require a zero dollar investment. Others require a one-time payment of $5 or so.
After completing the offer, depending on the FREE item of your choice, you'll need to refer your friends and associates to the site and have them complete an offer.
Now we've been doing this for some time and have received various FREE items including an Apple iPads (2), Apple iPhones (3), a Xbox360, a Playstation 3, and more.