Chametz is a Hebrew term that refers to any food product that is made from one of the five grains (wheat, barley, spelt, rye, or oats) and has been allowed to ferment or rise. During the holiday of Passover, Jews are prohibited from consuming or owning any chametz, as it is considered leavened bread and is therefore not allowed to be eaten or even seen during the holiday.
The prohibition against chametz during Passover is based on the biblical commandment to eat matzah, which is an unleavened bread that is made from flour and water and is baked quickly to prevent it from rising. According to Jewish tradition, the Israelites were in such a hurry to leave Egypt that they did not have time to let their bread rise, and so they ate matzah instead.
In order to prepare for Passover, Jews are required to remove all chametz from their homes and possessions. This process is known as "bedikat chametz" and involves a thorough search of the home to ensure that no chametz is left behind. Any chametz that is found must be either eaten, burned, or sold to a non-Jew before the start of the holiday.
During Passover, Jews eat only matzah and other foods that are made without chametz. This includes foods such as matzah ball soup, gefilte fish, and potato kugel. In addition, many Jews also avoid eating kitniyot, which are legumes and other foods that are not chametz but are also prohibited by some Jewish communities during Passover.