A soufflé is a light, fluffy baked dish made with egg yolks and beaten egg whites combined with various other ingredients and served as a main dish or sweetened as a dessert. The word soufflé is the past participle of the French verb souffler which means "to blow up" or more loosely "puff up" — an apt description of what happens to this combination of custard and egg whites.
Every soufflé is made from 2 basic components:
The base provides the flavor and the whites provide the "lift". Common varieties for the base include cheese, chocolate, and lemon (the last two used for desserts, with a good deal of sugar). When it comes out of the oven, a soufflé is generally very large and fluffy, and will "fall" after 20 or 30 minutes (as risen dough does).
Soufflé can be made in containers of all shapes and sizes, but it is traditional to make soufflé in "soufflé cups" or ramekins.