Hello, Jacqueline,
With the Disney Dining Plan, each adult on the meal plan will get an entree, a nonalcoholic beverage, and a dessert at a table service restaurant or a buffet meal. A quick service meal will consist of an entree (or combo meal), nonalcoholic beverage, and dessert.
Children ages 3-9 on the Disney Dining Plan will have the same options, but they will need to order off the children's menu and will be able to also order an appetizer at lunch and dinner.
In addition to your meals, each person on the plan will receive a refillable drink mug and will also have a snack a day.
Gratuities are not included except at Dinner Shows, Private In-Room Dining and Cinderella's Royal Table.
To read about all of your dining options, you can look through the
2012 Disney Dining Plan brochure or the
2013 Disney Dining Plan brochure (which does have a few differences in restaurant selection).
Once you are at WDW, cast members will be able to help you with any questions you may have. All the servers at the restaurant are incredibly helpful with the Disney Dining Plan.