Kosher foods are divided into three categories: meat, dairy and pareve. One of the basic principles of kashrut is the total separation of meat and dairy products. Meat and dairy may not be cooked or eaten together.
"Mixtures of milk and meat are prohibited according to Jewish law. This dietary law, basic to kashrut, is based on two verses in the Book of Exodus, which forbid "boiling a (kid) goat in its mother's milk" and a third repetition of this prohibition in Deuteronomy" (Wikipedia).

According to the Talmud, these three almost identical references are the basis for three distinct dietary laws:

  • the prohibition against cooking a mixture of milk and meat
  • the prohibition against eating a cooked mixture of milk and meat
  • the prohibition against deriving any benefit from a cooked mixture of milk and meat.

. To ensure this, the kosher kitchen contains separate sets of dishes, utensils, cookware, and separate preparation...