The Hebrew word kosher means "fit." The kosher laws define the foods that are fit for consumption for a Jew.
The kosher laws were commanded by G‑d to the Children of Israel in the Sinai
desert. Moses taught them to the people and wrote the basics of these
laws in Leviticus 11 and Deuteronomy 14; the details and particulars were
handed down through the generations and eventually written down in the Mishnah
and Talmud. To these were added various ordinances enacted through the
generations by the rabbinical authorities as "safeguards" for the biblical laws.
Throughout our 4000-year history, the observance of kosher has been a
hallmark of Jewish identity. Perhaps more than any other "mitzvah," the kosher
laws emphasize that Judaism is much more than a "religion" in the conventional
sense of the word. To the Jew, holiness is not confined to holy places and
times outside the everyday; rather, life in its totality is a sacred endeavor.
Even the seemingly mundane activity of eating is a G‑dly act and a uniquely Jewish experience.