There exists a set of dietary rules in the Jewish tradition that are expected to be followed by all believers.
Basically, for people having faith in Judaism, it is a very deep belief that meat of only certain animals can be eaten. Kosher rules are recommended according to Jewish dietary laws and some regard it to be difficult. Most of the dietary laws are believed to have found their origin in the Bible.
The rules are same for all Jewish followers irrespective of the country. However, their food system adapts to various inevitable factors like ingredients available in the respective country and production of food.
Many people have a false assumption that kosher foods are blessed by the "rabbi" and hence they can be eaten. On the contrary, they are the ones that have been recommended by the Jewish dietary laws.
As per kosher laws, any food is generally divided into 3 parts, that is meat, dairy, and pareve. Meat and dairy foods can't be eaten or prepared together. While meat is used to indicate anything derived from animal flesh, dairy foods comprise products from cow's milk.
Pareve, on the other hand, is categorized between animal flesh and fruits; for instance, eggs, fruits, candies, and vegetables. Generally, the categorization of pareve foods is complex and not clearly defined.
A short list of some food items is as follows:
Fish (that can be removed without tearing the flesh)
Certain animals such as cow, goat, giraffe, antelope, and deer.
Poultry animals like chicken, turkey, goosem and duck are allowed to be eaten.
Forbidden birds are not allowed to be consumed. Although the criteria for forbidden birds is not very clear. Scavenger birds and preys are generally categorized as "forbidden" birds.
Fish can be eaten if it has fins and scales that are detachable from the skin.
Furthermore, it's very important that all the blood must be drained before the meat is cooked. That is why kosher salts have become increasingly popular.
Generally, it's imperative that both meat and dairy products are cooked in separate utensils. It's customary to have separate vessels for both these types of food and they are never mixed.
Slaughtering an Animal
Slaughter of weak and diseased animals is discouraged. Moreover, the animal must be slaughtered in the most humane manner possible. Generally, cutting the throat with a sharp knife is recommended and the knife must not be old or worn out.
Since the rules enshrined in kosher cover a wide range of laws, it is tedious to be aware of its each and every aspect. However, the rules mentioned here, that is those related to dietary rules or "kashrut" must be strictly followed by a Jew. For children also, all rules are the same and they are generally able learn the practices and rituals while growing up.