I looked it up, and it appears that the main difference is the shape of the pan. One site said that tarts are always open-topped and have a thin crust. They are baked in a tart pan or a straight-sided low pan or dish. Pies can be covered or uncovered, and they are baked in a sloping pan or dish. One site said that tarts are always removed from the pan, but pies aren't. But my grandmother usually removed her pies. So after having read all of this, I'd say if the sides are straight up and it is served out of the pan, it would probably be a tart.
at 8:59 AM on Dec. 21, 2008