"Kosher" is the term used to describe food prepared in accordance with the dietary guidelines of Jewish law. Kosher foods are not 'blessed' by rabbis or other religious officials. Food that is not kosher according to Jewish law is referred to as "treyf."
There is some disagreement over why Jewish people eat kosher foods. The spiritual text of Judaism, the Torah, describes the kosher diet, and followers of this text often follow this set of dietary guidelines. Others, however, may follow a kosher diet simply because of its proposed health benefits.
Certain animals may not be eaten at all. This restriction includes flesh, organs, eggs and milk of the forbidden animals. According to the Torah, any animal that has cloven hooves and chews its cud is acceptable to eat, including sheep, cattle, goats and deer. Any animal that does not have both of these qualities is not allowed, including, camel, the hare and pig.
Seafood can only be eaten if it has fins and scales. Shellfish, such as lobsters, oysters, shrimp, clams and crabs are not kosher.
Of the animals that may be eaten, the bird and mammals must be killed in accordance with Jewish law. Animals that die of natural causes or are killed by other animals are not allowed to be eaten. There must be no disease or flaws in the organs of the animal at the time of slaughtering.
Ritual slaughter is referred to as "shechitah." The person that performs the slaughter is known as the "shochet." The method of slaughter is a quick, deep stroke across the throat with a perfectly sharp blade. This form of slaughtering also allows for the rapid drainage of blood.
In regards to birds, the Torah does not list guidelines. Rather, it just lists birds that are forbidden. The only birds permitted are chicken, geese, duck and turkey.
All reptiles are forbidden by Jewish law.
All blood must be drained from the meat or broiled out of it before it is eaten.
Certain parts of permitted animals are not allowed to be eaten.
Meat cannot be eaten with dairy. Fish, eggs, fruits, vegetables and grains can be eaten with either dairy or meat.
Utensils that have come into contact with any meat cannot be used with dairy.
Utensils that have come in contact with a non-kosher food cannot be used with a kosher food and vice versa.
Grape products made by non-Jewish people may not be eaten.
Combining fish and meat
The Talmud and Yoreh Deah suggest that eating meat and fish together may cause a disfigurative condition Strictly Orthodox Jews thus avoid combining the two, while Conservative Jews may or may not avoid this.