Some Jewish holidays have special rituals, like the Seder of Passover or the sukkah, lulav and etrog of Sukkot. In the Torah, there are no rituals like that for Shemini Atzeret. But starting at the time of the Talmud, Shemini Atzeret became the holiday for finishing the annual reading of the Torah in the synagogue. The celebration of that—called Simchat Torah— has become the main feature(def. n2) of the holiday.