TIW is a discount card you can buy if you have an annual pass. You only need one card per family, and I think it was $65 when we bought our last one (that's always subject to change though). It gives you 20% off at many WDW and resort restaurants. We found it matched our dining habits quite well. We have had the TIW (DDE) card for 3 years, and much prefer using that over the dining plan.