Kelly, I know this can be confusing, but I hope I can clear it all up for you.
Disney's PhotoPass service is a great way for the wonderfully talented photographers around the parks to capture those memories in many iconic locations such as in front of Cinderella's Castle in Magic Kingdom or Spaceship Earth at Epcot among many others. When the photographer offers to take your photo, this is complimentary, with no obligation to buy, unless you want to purchase the photos that are taken. You can do this in several ways. You can either purchase the Photo CD (which would include all the photos taken on your PhotoPass card) or you can purchase individual photos either digitally or in the form of prints.
Another option is
Disney's PhotoPass+. With this special offer, you purchase the PhotoPass+ and it includes all your PhotoPass images taken during your vacation, plus any photos taken on select attractions and dining locations (see the link I have provided to get info on those exact locations). The PhotoPass+ also includes a gallery of stock photos around the Walt Disney World Resort. All of this is included along with a special code to redeem your photo CD once you return home from your vacation. You will receive a special lanyard and PhotoPass+ card to use at the various PhotoPass locations. One great thing about it is that if your party separates at any time during your trip, you can just get another general PhotoPass card and when redeeming your PhotoPass+ card at the end of your trip, you can also add the photos taken on the other card as well using its code.
I hope this clarified the process. Say "cheese" and have a vacation full of memories!
~Allison L