"Kosher" signifies food that complies with the dietary rules of which religion?

Lorraine , jews, muslims and christians lived in Palestine in peace longer than that, exactly until the state of Israel was created. Amongst the descendants of the jews who have been living in Palestine for centuries, there are many who don't recognize the state of Israel, and even hang the palestinian flag in their homes. For this, they are treated very badly by the israeli authorities, and even by other jewish civilians.