Изучайте: https://ru.wikipedia.org/wiki/%D0%9F%D0%BE%D1%82%D0%B5%D1%80%D0%B8_%D1%81%D1%82%D0%BE%D1%80%D0%BE%D0%BD_%D0%B2_%D0%BF%D0%B5%D1%80%D0%B8%D0%BE%D0%B4_%D0%B2%D1%82%D0%BE%D1%80%D0%B6%D0%B5%D0%BD%D0%B8%D1%8F_%D0%A0%D0%BE%D1%81%D1%81%D0%B8%D0%B8_%D0%BD%D0%B0_%D0%A3%D0%BA%D1%80%D0%B0%D0%B8%D0%BD%D1%83