The Torah tells us about the laws of kashrut in Leviticus, when the Israelites gathered up around Mount Sinai to receive the 613 commandments at the heart of all Jewish practise. In the days just before the revelation at Mount Sinai, it was not clear which meats would be forbidden, and the Israelites were restricted to vegetable and dairy products.

The majority of kosher food is not in fact eaten by Jewish people. Kosher food is acceptable under a Muslim halal diet and, because of the seperation of milk and meat, vegetarians often eat in dairy kosher reataurants. Kosher food production is overseen by a supervisor called a Mashgiach.
The Mashgiach is an expert in the laws of kashrut. Animals used for meat must have split hooves, and chew the cud. Fish must have fins and scales. Birds of prey are not allowed. Stringent laws require that meat and dairy be prepared and kept seperately, and Jewish homes often have a large kitchen with dstinct spaces for meat and dairy cooking.

Spiritual Thanks:
It is said that when one drinks half a cup of water the remaining water breathes a sigh of relief, but that when the drink has been blessed, the remaining water is a bit jealous. Sanctification plays a major role in Jewish life. It is part of the Jewish purpose to bring sanctity to all areas of one's life, and since G-d has been so generous and created a natural order of abundance, we thank G-d before and after each meal and snack.
A verse in Deuteronomy says: "Man does not live on bread alone, but by the utterance of God's mouth does man live." The great Maggid of Mezrich explains, hunger is a hunger for Gods word that brings everythng into being. When we eat, we redeem the innate spiritualism of the food.
"And you shall sanctify yourselves and be holy." This is how the Torah concludes the laws on Kashrut. In Hebrew the word for holy, kadosh, also implies removal or separation. By keeping the laws of Kashrut we distinguish ourselves from the physical world, bringing sanctity to the life-sustaining but otherwise mundane activity of eating. We are restricted, and this continually brings us back to the greater purpose in our lives: creating spiritual meaning, lovingly sharing G-d's guidance and becoming "a light unto the nations", the fulfillment of G-d's promise to our forefather Abraham.
When we work, sleep and eat merely to work, sleep and eat we are no different from animals, who do not go through this world with the miraculous gifts of intelligence and choice. But when we eat to serve a higher puporse, we imbibe G-d's love and wisdom and build a heaven on this

B'tei avon!