The Hebrew word kosher means fit or proper as it relates to kosher dietary law. Kosher foods are permitted to be eaten, and can be used as ingredients in the production of additional food items.

The basic laws of Kashrus (a Hebrew word referring to kosher and its application) are of Biblical origin (Leviticus 11 and Deuteronomy 17). For thousands of years, Rabbinic scholars have interpreted these laws and applied them to contemporary situations. In addition, Rabbinic bodies enacted protective legislation to safeguard the integrity of kosher laws.

The laws of kashrus are complex and extensive. The intention of this guide is to acquaint the reader with some of the fundamentals of kashrus and provide insight into its practical application. Given the complex nature of the laws of kashrus, one should consult an Orthodox Rabbi whenever a kashrus issue arises.

Though an ancillary hygienic benefit has been attributed to the observance of kashrus, the ultimate purpose and rationale is to conform to the Divine Will, as expressed in the Torah.

Not too long ago, most food products were made in the family kitchen, or in a small factory or store in the local community. It was relatively easy to ascertain if the product was reliably kosher. If Rabbinical supervision was required, it was attended to by the rabbi of the community, who was known to all. Today, industrialization, transcontinental shipping and mass production have created a situation where most of the foods we eat are treated, processed, cooked, canned or boxed commercially in industrial settings, which can be located hundreds or thousands of miles away from home.

What adds further complication is that it is generally not possible to judge the kosher status of an item on the basis of the information provided in the ingredient declaration for a variety of reasons.

First, the product may be made from kosher ingredients, but processed on non-kosher equipment. Second, the USDA does not require the listing of certain processing aids, such as pan liners and oils that serve as release agents. Though not legally classified as ingredients, these items could nonetheless render the product non-kosher. Third, many ingredients can be kosher or non-kosher, depending on their source of origin. For example, glycerin and emulsifiers are made from either vegetable or animal oils. Finally, many ingredients are listed only in broad terms, with no breakdown of the many complex components that make up the actual item. For example, a chocolate flavor may contain 50 ingredients, but the ingredient declaration will list this entire complex of ingredients as "flavors".

Unless a person is an expert in food production, the average consumer cannot possibly make an evaluation of the kosher status, which is why it is important to purchase only those products that have the endorsement of a reliable kosher agency.