A pie is a baked dish which is usually made of a pastry dough 
Oh, I like pie!  Apple pie especially.
They have casing that covers or completely contains a filling of various sweet or savoury ingredients.
I prefer sweet pies to savory pies.  
funny enough,  Pies are defined by their crusts
Which is the best part, especially if it's flaky!
a pastry or other covering before baking. A "two-crust" pie has the filling completely enclosed in the pastry shell. Shortcrust 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.
History.
The need for nutritious, easy-to-store, easy-to-carry, and long
Pie
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 has the filling in the bottom of the dish and is covered with