The difference between a pie pan and a tart pan is more than simple semantics. A pie pan, often called a pie plate, pie dish, or pie tin, is a round, shallow, slope-sided dish with a flat or fluted rim to hold the edge of a pie crust. While the most popular American pie pan is made of Pyrex glass, pans made of aluminum, tin, heavy black steel, and fired clay are also available. Most pie pans are one piece, although some steel pie pans have removable bottoms.
A standard pie pan is 9 inches in diameter and 1-1/4 inches deep. There are 9-1/2- and 10-inch pans, as well as small (4-1/2-inch) individual pie pans; it's important to read your recipe for the right size. (Measure across the inside rim.) Deep-dish pie pans are 1-1/2 to 2 inches deep.
The main difference between a tart pan and a pie pan is the shape and depth of the sides. A tart pan has straight sides (some fluted, some not) that turn out neat, more "professional" looking pastries than the slope-sided pie pans. Most tart pans are made of metal, and the best have a removable bottom, allowing you to slip off the outer ring without marring the beautiful crust.
Unlike pie pans, tart pans come in an endless variety of shapes and sizes. They may be round or rectangular, and they range from 4 to 12 inches across and from 3/4 to 2 inches deep. (Smaller than 4 inches would be a tartlet pan.)
Tart pans come in many shapes and sizes. This assortment includes a flan ring (at left) and a ceramic quiche pan (second from left).
In place of a tart pan, some bakers use a tart ring, also called a flan ring. This thin metal circle (1/2 to 1 inch deep and in varying diameters) sits directly on a baking sheet, resulting in a much crisper bottom crust. Rings are especially good for savory tarts without a lot of sugar in the crust (a sweet crust will brown during baking no matter how it's formed).
Round tart pans are also sometimes referred to as quiche pans. With their upright sides, you get more filling into the shell and a neater, more regular slice of quiche when serving. Quiche is also sometimes baked in a ceramic or fired clay pan that resembles a tart pan but that doesn't have a removable bottom. While it's slightly more difficult to get the first slice of quiche out of one of these pans, some bakers believe the material (especially if unglazed) bakes superior crusts. These pans double as serving dishes.