A pie is a baked dish which is usually made of a pastry dough casing that covers or completely contains a filling of various sweet or savoury ingredients.
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, which may also be called a cobbler, has the filling in the bottom of the dish and covered with a pastry or other covering before baking.
A two-crust pie has the filling completely enclosed in the pastry shell.
Flaky pastry 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 ones designed for multiple servings. A pie is a baked dish which is usually made of a pastry dough casing that covers or completely contains a filling of various sweet or savoury ingredients.
A tart is a baked dish consisting of a filling over a pastry base with an open top not covered with pastry. The pastry is usually shortcrust pastry; the filling may be sweet or savoury, though modern tarts are usually fruit-based, sometimes with custard.
Flan, in Britain, is an open pastry or sponge case containing a sweet or savoury filling. A typical flan of this sort is round, with shortcrust pastry.