The crust is the bread base of a pizza. It is a main ingredient of pizza.
The bottom of the pizza, called the crust, may vary widely according to style—thin as in a typical hand-tossed Neapolitan pizza, or thick as in a deep-dish Chicago-style. It is traditionally plain, but may also be seasoned with garlic or herbs, or stuffed with cheese. The outer edge of the pizza is sometimes referred to as the cornicione. Often pizza dough contains sugar, both to help its yeast rise and enhance browning of the crust. Dipping sauce specifically for pizza was invented by American pizza chain Papa John's Pizza in 1984, and has since become popular when eating pizza, especially the crust.
The outer crust is the portion of the crust that does not contain toppings. New York style pizza and Thin Crust pizza is often held from the outer crust, often folded. Pizza with cheese and occasionally some toppings like pepperoni in its outer crust is stuffed crust pizza.