At WDW the meal plan is on your park hopper. You get one counter service meal, one snack and a table service meal. You are given a credit for each. Very simple. At DL, they give you vouchers. Character meals get a voucher. Some of the other table service uses these vouchers as well. However, if you exceed the value of a character meal while at a table service rest., they will charge you the difference. For counter service, they give you vouchers that range from $5-10. If you have change that should come back to you, you do not get it. So if you spend $6 and you give them $10 voucher, you eat the $4
That's why many here on the Dis use Disney Dollars or Disney gift cards to help "prepay" for their meals. That's what we did. We had Disney Dollars and gift cards plus, we did prepurchase the character meal vouchers. There are various places to buy these, WDT, GAT, Ares.