Yom Kippur. Yom Kippur is a holiday celebrated by all Jews and it's one of the most important holidays of the Jewish year. The name Yom Kippur means day of Atonement.The day is set aside to afflict the soul to attone for the sins of the past year. No work can be performed on this day and you are supposed to refrain from eating and drinking on that day. This holiday begins before sunset on the evening before Yom Kippur and ending after nightfall on the day of Yum Kippur.