Kosher means feasible or ritually appropriate. The law is derived from the Torah, which explicitly defines which animals are permitted as food and which are forbidden. The characteristic signs of the kosher mammals are fully cloven hoofs and chewing the cud. Cattle, sheep, goats and gazelles for example meet these criteria. Non-kosher mammals are pigs, camels, horses, donkeys, rodents and others. The Bible also names species of birds that are and those that are not kosher. Barn fowl, ducks, geese, pigeons, pheasants and turkeys are permitted. On the contrary, birds of prey, scavengers and bats are forbidden. Kosher fish must meet both basic requirements – they must have both scales and fins. Totally prohibited are all reptiles, amphibians, molluscs, crustaceans (fruits de mer) and insects. No blood or meat of animals that died from natural causes may be eaten. The animal to be slaughtered must be healthy. Animals to be eaten thus must be slaughtered in a prescribed ritual way, minimizing their pain. The basic rule of kashrut forbids eating meat together with dairy products, which is why in assessing the propriety of an article of food or drink all the ingredients are checked. All vegetables and fruits are allowed only after making sure they do not contain insects or worms.
For a list of eligible food, which can be generally bought in shops, see http://www.kehilaprag.cz/mambo/docs/kosher_cz_052008.pdf.