Kashrut (keeping kosher) is a set of laws that was given to Moses by G-d. Keeping kosher means following these many laws and not just simply refraining from eating pork or shellfish. Many people have tried to find the reasons G-d commanded that the Jews keep kosher but kashrut is one of many mitzvot from G-d that do not have any rational explanations. This does not mean however, that Jews can simply dismiss these laws.

The main purposes of Kashrut are:
1. to limit the number of animals the Jew is permitted to kill and eat;
2. to render the slaughter of the permitted animals as painless as possible;
3. to cause revulsion at the shedding of blood;
4. to instill self-discipline in the Jew;
5. to help sustain Judaism and the cohesion of the Jewish community; and
6. to raise the act of eating from an animal-like level.

The kosher animals that may be partaken of by the Jews (such as the cow, chicken, and certain locusts) must have certain characteristics. Land animals must have split hooves and chew their cud, fish must have both scales and fins, and birds may not be birds of prey. Even if the land animals are kosher, certain parts of the animal (the sciatic nerve and its adjoining blood vessels as well as the chelev) may not be eaten. The non-kosher animals that may not be partaken of by the Jews (such as the pig, rabbit, and eagle) do not have these characteristics. A shochet must follow certain laws regarding how animals are to be slaughtered and how the meat must be prepared in order for the clean animals to be considered kosher. The shochet must ensure that the animal has no broken bones and the knife being used must be totally free of any nicks or imperfections. The animal must have its throat slit in a specific area with one stroke to ensure the least pain for the animal. All the blood must be drained and salt is used to help ensure that any further blood will be soaked up before the meat is ready for purchase. In addition to these differences between kosher and non-kosher food there is the prohibition of mixing dairy and meat. This prohibition includes all milk-producing mammals but excludes fish. Originally fowl was not considered "meat" in the sense that fowl does not produce milk. However, rabbinic rulings have now prohibited mixing dairy and fowl.

The status of kosher, treif, and pareve also extends to utensils, plates/bowls, pans, cooking, cooking and cleaning surfaces, fuits and vegetable, and drinks such as wine, grape juice, soda, milk, and alcohol. All utensils, plates/bowls, pans, and cooking and cleaning surfaces must be rendered kosher in order for the food to retain its kosher status (see: How to make your kitchen kosher). The concept of bishul Yisrael demands that a Jew be involved in the cooking or processing of food in order for the food to be considered kosher. All fresh fruits and vegetables are kosher. However, it is important to thoroughly inspect them to ensure there are no bugs or worms on the fruits and vegetables since most of them are not kosher. When it comes to wine and grape juice, the process of mevushal ensures that the wine and grape juice is kosher. Cholov Yisrael is an ancient practice that involves a Jew being present from the time of milking from a kosher animal (such as a cow) until the time of bottling to ensure that the milk from the kosher animal will not be mixed with milk from a treif animal. In the United States, most rabbis consider all milk to be kosher because of the strict regulations placed on the milking industry.

The general rules of kashurt are:
1. Certain animals are forbidden;
2. Certain parts of the animals are forbidden;
3. All blood must be removed from the meat before it may be eaten;
4. Animals must be slaughtered in accordance with halachah;
5. Fresh fruit and vegetables are permitted but must be checked for bugs;
6. Meat (flesh of any animal) may not be eaten with dairy;
7. Separate dishes, utensils, cooking areas, and pots/pans must be used for meat and dairy;
8. Grape products made by non-Jews are forbidden.