We never not use the dining plan. It's the simplest way to dine in WDW. You and each guest in your party will receive the following everyday:
1 Table Service - basically, sit-down dining where you'll be served; you get appetizer, entree, dessert, non-alcoholic beverage (even the kids get an appetizer)
1 Counter Service - you serve yourself; you get entree, dessert, non-alcoholic beverage
1 Snack - these are fruits, beverages, popcorn, ice-creams, etc.
You do not have to use each one each day. Say you're staying for 4 days...well, you will get 4 of each per person. You could have 2 TS in one day. You could use all of your snacks in one day. It really doesn't matter how you use them. You'll just receive 4 TS, 4 CS, 4 Snacks per person. There are some restaurants/shows where you would have to use up 2 TS in order to dine there. You can go to WDW site and get all the information and the participating restaurants. You should definitely plan your dining well before you leave to go to WDW.