Chametz is "leaven" -- any food that's made of grain and water that
have been allowed to ferment and "rise." Bread, cereal, cake, cookies, pizza, pasta, and beer are blatant examples of chametz;
but any food that contains grain or grain derivatives can be, and often is, chametz. Practically speaking, any processed food that is not certified "Kosher for
Passover" may potentially include chametz ingredients.
Chametz is the antithesis of matzah, the
unleavened bread we eat on Passover to recall the haste in which we left Egypt, and the humble faith by which we
merited redemption. Matzah is the symbol of the Exodus, a central component of the Seder
rituals, and the heart of the "Festival of Matzot" (as Passover is called in
the Torah). And the flip-side of eating matzah is getting rid of chametz
-- and the egotism and spiritual coarseness it represents.