The Jewish word “Kasher   ” indicates the food in compliance with the Jewish alimentary norms. Some quadrupeds, birds and fish are forbidden and in the same moment cannot be eaten foods made of meat with foods made of milk .  
Kasher wants to say simply what it is allowed because pure, proper, suitable.  

Rules for the aliments of the Jewish kitchen.
The fact that the Hebrews from twenty centuries live scattered in the world explains because uses and customs vary from country to country. The ritual changes according to the Jewish communities have seat in the Mediterranean basin (Sefardite Community), in the Center-East Europe (Ashkenazite Community) or in the Levant (Levantine Community).
The way to prepare foods changes in the various communities even if for this kitchen there has been an evident process of assimilation with the dominant society.
“To cook Kasher”, for the observant Hebrews does not want only to mean to maintain a tradition, to safeguard some hygienic norms, but has also the meaning to sanctify (Qedushah).

Like all Hebraic precepts, that spur to cover of sacrility every action of the daily life, also cooking kasher acts as stimulus to the inner search. This precept is carried out with the “shechità” or Hebraic ritual slaughtering that consists in killing the animal with a single cut of the most sharp knife and with very precise measures, from the trachea to the esophagus, so as to provoke the immediate death and the complete bleeding.
Beyond to the shechità, who executes the slaughtering, must provide to the “bedicà”, that is, to an accurate visit of control of the killed animal because in case turn out sick or imperfect the animal is not kasher and therefore cannot be used.
Afterwards will follow “nikur” or elimination of the sciatic nerve.
Subsequently on proceeds to the elimination of some parts of fat of the meat (chelev).

The “melihà” (put under salt): the meat well rinsed must be put under coarse salt for at least twenty minutes and not more than one hour. After the salting the meat must be washed under running water for two or three times in order to eliminate the blood completely, or putting the meat to grill, in such way the blood drains in the below container.

The liver will be roasted because the salting is not sufficient to eliminate the blood, while the brain and the heart will be put under salting after having them opened and well cleaned.