"Bar" is the form and the dish could be brownies, or lemon bars.
"Cookie" is the form, even though the construct could be the same ingredients and method as "Bars."
"Custard" is a form that relates to the soft combination of sweetener, no-grain binders, sometimes fat and flavoring. Lemon, chocolate, banana cream custard being the dishes.
"Pudding" is a form that uses a grain binder, rice and bread pudding being the dishes.