A pie is a baked dish which is usually made of a pastry dough casing that contains a filling of various sweet or savoury ingredients. Sweet pies may be filled with fruit, nuts, brown sugar, sweetened vegetables, or with thicker fillings based on eggs and dairy . Savoury pies may be filled with meat, eggs and cheese or a mixture of meat and vegetables .
Pies are defined by their crusts. A filled pie (also single-crust or bottom-crust), has pastry lining the baking dish, and the filling is placed on top of the pastry but left open. A top-crust pie has the filling in the bottom of the dish and is covered with a pastry or other covering before baking. A two-crust pie has the filling completely enclosed in the pastry shell. Pâte sucrée is a typical kind of pastry used for pie crusts, but many things can be used, including baking powder biscuits, mashed potatoes, and crumbs.
Pies can be a variety of sizes, ranging from bite-size to those designed for multiple servings.