o What may be eaten and what may not be eaten,
o Separation of meat from diary, and
o How certain foods are prepared

I found that there is usually a practical reason and a religious reason for the Kosher laws. For example, shellfish are not kosher. The religious reason is that shellfish are scavengers and all scavengers are not kosher. The practical reason is that the kosher laws were made before refrigeration and shellfish spoil very quickly, especially in the heat of the Middle East. So avoiding shellfish was a good idea for staying healthy in biblical times.

The religious reason for the separation of meat and dairy is that dairy represents the mother and meat represents the child and that you should never take the mother and the child in the same meal. Practically, it is more difficult for the body to digest meat and dairy at the same time.