Thanks, Stephanie! Love right back atcha! Disney's PhotoPass service allows guests to have their pictures taken at various hot spots in the parks. One of the perks is that your whole family will appear in the photo together, rather than leaving someone out behind the lens. As for purchasing the CD, it can be done either before or after your trip. I would recommend
pre-purchasing, though, because it will save you about fifty dollars. Even better news is that it's a risk free purchase; you can get a full refund if you decide you don't like the pictures once you've returned home. Win-win, right? Follow the link I included above to pre-purchase your CD. Once you're in the parks, just approach a PhotoPass photographer when you see one and ask that he or she take your photo. He or she will give you a PhotoPass card that you can keep and reuse. Each and every time you have your photo taken, present the card so that your pictures can be scanned onto it. When you get home, go online and enter your card number and your photos will all be displayed. You can just enter the unique code you got when you pre-purchased the CD and your disc will be shipped, with the digital versions of your photos loaded onto it. Easy peasy!
I hope that clears things up for you.