The way this works is when NCP has a scanner available for your area, they will send you a scanner to scan your purchases. After your purchases are transmitted, you earn points. You can then redeem these points (once you build them up obviously!) for great rewards, everything from little things to Xbox 360s and vacations!
You are also entered into regular sweepstakes when you are regularly scanning and transmitting your purchases. I did this for about a year and actually won some money through the sweeps too!