The basic
DDP which costs $37.99/day/adult includes one snack/day, one counter service meal/day, and one table service meal/day (appetizers and gratuity not included).
The DxDDP which costs $69.99/day/adult includes a resort mug for everyone in the room, two snack credits/day and three meal credits/day, which can be used for counter service meals or table service meals in any combination you choose (3 one credit TS meals/day, 3 CS meals/day, 1 one credit TS, then a two credit signature restaurant/day, one CS then a two credit signature restaurant/day, etc). The DxDDP does include the appetizers, but gratuity still not included.
The DxDDP is very flexible and can be used any way you want. For example I am using it for both my trips in May and in Sept, but am using it different each trip. In May I am going solo and have always wanted to try all the two credit Signature restaurants, so am eating an early lunch everyday at a one credit TS restaurant, then using two credits every night at a Signature restaurant. In Sept I am traveling with a diabetic who must eat three meals/day, so we are doing a one credit TS restaurant three times a day. With the DXDDP you don't even have to step foot into a CS restaurant if you don't want to. However, if you want you can also use those same three credits I'm using at TS restaurants for CS restaurants. The choice is yours whether you use your 3 credits/day as CS or TS.