The big picture on Kashrut

From Talia Friedman:
I learned all the halachot, but I'm still not sure how to explain to a Reform Jew what kashrut is and why it is kept.

Before addressing the kashrut issue itself, I'd like to comment on the fact that you asked this question at all. One of the pitfalls that Jewish day school educators have to watch out for is the focus on details while ignoring the fundamentals. It's important to leave a class in kashrut and know all the terms - bitul, nat bar nat, ben yomo, and know how to analyze cases, but it's also important - equally if not more so - to take a step back and think about why we're doing what we're doing. This applies not only to kashrut, but to Shabbat, davening, Torah learning and all the behaviors and beliefs that make up the life of an Orthodox Jew.

About kashrut specifically - one can say, briefly, that the Torah restricts certain foods based either on what kind of food it is (types of animals, for example) or the way the food is prepared (e.g., must be slaughtered properly, meat and dairy cannot be mixed).

As for the why - many rishonim consider kashrut in the category of chukkim - mitzvot for which there is not necessarily a satisfactory rational explanation, but which are performed as part of our service to Hashem. However, many explanations have also been offered, and here I think there is license to accept whichever one speaks to you the most. Rambam (Moreh Nevuchim III:48) famously gives a health explanation for kashrut (although he might have reconsidered had he visited World of Goodies). Ramban, based on the pesukim that describe certain foods as causing "timtum ha-lev," dulling of the heart, says that the nature of certain predatory and carnivorous animal species can be absorbed by us when we eat them. The Torah mandates avoiding the consumption of these aggressive animals so that our own natures will remain gentle. Another explanation is: kashrut is a mark of distinction of the Jewish people, so that one who must eat foods different from his gentile collegues will constantly remain aware of his or her religious identity. Finally, one can view kashrut as taking one of life's most mundane and physical activities, eating, and elevating it with the discipline of being conscious of Hashem's commands every time we put food in our mouths.