They're not dining plans per se, but rather all-inclusive resort packages. Being two different plans, there are obviously different inclusions, but in general they provide unlimited and pre-paid access to resort amenities, such as golf, tennis, boating, horseback or carriage rides, etc., and even some of the child care services (kid's clubs) and in-room babystitting (Platinum only).
They also contain a dining component which can essentially be thought of as "DxDP on steroids". Like DxDP, they include 3 meal credits and 2 snack credits per person per night, however, all meals cost only 1 credit (even signature meals, dinner shows, CRT, and the like), and additional restaurants are included (Portobello's, Fulton's, RFC, even Victoria and Albert's on Platinum).
The costs are higher than DxDP, accordingly.