For each night of your stay each person in your room will receive:
1 counter service (quick service) meal which includes your entree, a drink and a dessert or a combo with drink and dessert (some examples of quick service restaurants is Cosmic Ray's in MK, Tusker house in AK, the resort food courts).
1 Table service meal which includes an appetizer, entree, drink and dessert AND tax and tip (18%) or a buffet with beverage and tax and tip (18%). Some examples include Le Cellier, Kona Cafe, Crystal Palace, Boma's, and Mama Melrose. Some signature restaurants require each person to use 2 table service "credits" to enjoy 1 meal (such as Narcossee's, Artist Point and Brown Derby).
1 Snack which is generally most items under $4.00 such as bottled water, popcorn, mickey bars, fruit, danish, donuts, candy, ice creams (it really is a very long list).
You can use your credits in any order you like (i.e. 2 table service meals one day, 3 counter service meals the next).
I would suggest if you do book the dining plan that you make sure to make most (if not all) of your dining reservations in advance to ensure that you can enjoy the restaurants of your choosing.
If you have any specific questions, please - ask away.