Kosher foods must come from a certified body (i.e. a Rabbi). Kosher does not allow the consumption of flesh, organs, eggs, and milk of forbidden animals (hare, camel, and pig), and there is no mixing of meat and dairy.
Fruit and vegetables can be eaten but must be inspected for bugs, which are forbidden. Utensils or cookware that has been used with non-kosher hot food cannot be used with kosher food.
The word kosher, literally meaning “clean” or “pure,” refers to food that has been prepared in accordance with Jewish rules and rituals so it can be eaten by religious Jews.
Because the Torah allows eating only animals that both chew their cud and have cloven hooves, pork is prohibited. So are shellfish, lobsters, oysters, shrimp and clams, because the Old Testament says to eat only fish with fins and scales. Another rule prohibits mixing dairy with meat or poultry.
Jews can ensure they keep kosher by buying products certified as kosher with a mark called a hekhsher that usually identifies the rabbi or group that certified the product.
Foods so certified are not "blessed." Rather it means the place they were processed is inspected to make sure kosher standards are maintained. Kosher meat, for example, must be slaughtered without causing pain to the animal, meaning that death occurs almost instantaneously.
Approximately three-quarters of all prepackaged foods in the U.S. have some kind of kosher certification.
Reform Jews are not required to keep kosher but if they decide to, they can accomplish that by refraining from eating pork or shellfish, or just observing dietary rules at home, rather than when eating out, or by becoming vegetarians.