Yom Kippur is the holiest day of the Jewish year—a sacred time for fasting, prayer, confession, forgiveness, and return. This complete guide explains the meaning of the day, the five restrictions, Erev Yom Kippur preparations, Kol Nidrei, the five prayer services, Vidui, Yizkor, the Avodah, the Book of Yonah, Neilah, and the final shofar blast.