What's the difference between tart and pie?

Native speaker’s answer
Rebecca
A "tart" only has a bottom or base crust, which is usually thick. Whereas a "pie" has a crust on the bottom and the top, covering the filling completely. Ex: Jill's favourite part of the pie was the crust on the top. Ex: The tart filling was too sweet for Henry, so he just ate the crust at the bottom.