If you stay inside at Disney, you have the choice of pre-purchasing (or we got ours free in an offer which runs most years) a dining plan.
There are 3 levels:
Quick service. You get 2x QS credits and a snack credit per person, per night of stay. A quick service restaurant is a cafeteria style/self service style (or you get your food at the counter, then find a table to eat). The range of foods is enormous, it's not all burgers and chips.
Regular dining plan. You get 1 tables service and 1 quick service credit, and 1 snack credit per person per night of stay. A table service restaurant is a typical restaurant - waiter service. Again, huge range of styles, not all character meals (we go tongue character meals, but my dc are small and want to, and it saves queuing in the parks for meet and greet).
Deluxe dining plan. 3x meals credits per person per day. Plus 2 snack credits. Credits can be sued for either quick service or table service, as you choose.
You don't have to have a dining plan, you can just pay as you go. I don't think I'd buy a dining plan if I booked when the free dining offer wasn't running, but we've always had the free dining offer, and want table service meals, so it makes sense for us.