The word "kosher" means proper or acceptable, according to the Orthodox Union, the nation's largest kosher certification organization. Kosher laws originated in the Bible and govern Jewish dietary practices.
The Bible lists the food categories that are not kosher, including animals such as pigs, rabbits, shellfish and reptiles. Kosher species of meat and fowl must be killed in a prescribed manner, such as a cut by a sharp knife to the neck. The slaughter generally takes place under rabbinical supervision.
The rules prohibit Jews from eating meat and dairy at the same time, and they can't be manufactured together.
Passover has an extra layer of restrictions.
During the eight-day festival, Jews are not allowed to eat chametz, which includes anything made from wheat, rye, barley, oats or spelt. The only exception is matzo, a ritual flatbread that commemorates the Israelites' exodus from Egypt. Jews have been creative with matzo. They have turned it into flour to make cakes and cookies, meal for bread crumbs and the famous matzo balls, and farfel to use as a substitute for noodles and other starches.
Most Jews of European ancestry also avoid rice, corn, peanuts and beans because they were once commonly used to make bread. Their prohibition avoids any confusion.
Because so many distilled spirits are either derived, or have flavoring, from grains, they are generally not kosher for Passover unless certified by a rabbi that they don't contain forbidden ingredients. Kosher-for-Passover spirits may not be produced with equipment that's also used to make products with prohibited foods.
To be kosher at any time, wine must be made only by religious Jews.