Make a list of civilizations that originated in the Middle Ages. On what basis did the distribution of civilizations take place?

Make a list of civilizations that originated in the Middle Ages. On what basis did the distribution of civilizations take place? Why was it so important to people in the Middle Ages?

Islamic, Catholic, Orthodox, Indian, Far Eastern (Chinese, Japanese)
Civilizations were divided along religious lines. This was important for people in the Middle Ages, since it was religion that determined the picture of the world and the way of thinking of a person. If you were co-religionists, you understood each other and knew what to expect from each other, and if not, you were strangers who should be feared, and better killed.