Hi Karisa!
This is a great question! You can get more information on the various
Disney Dining Plans here. For the 2012 Standard Disney Dining Plan, you get one Quick-Service Meal, one Snack, and one Table-Service Meal per person, per night of your package stay for everyone in the party ages 3 and over. The plan also includes one Resort refillable drink mug per person, that is valid for the length of your stay (eligible for refills at Quick-Service locations only in your Disney Resort hotel).
So with a four night stay, you will get 4 Quick Service Meals, 4 Snacks, and 4 Table-Service Meals per person for everyone in the party ages 3 and over. You can use those meal credits whenever and however you would like. You will get them upon check-in and they expire at midnight on the day you check-out. For example, you can decide to use 3 Table Service meal credits on one day and save your Quick Service meal credits for another day. The secret is simply making sure that you use all of your meal and snack credits by midnight on the day you check-out.
I hope this helps! Please write back with more questions!