What is Yom Kippur?

Yom Kippur is theDay of Atonement
The holiest day in the Jewish New Year --
Yom Kippur (pronounced either"yahm-KIPP-er" or "YOME-kee-POOR", depending on regional accents) is a time of serious reflection and repentance, the most solemnday on the Jewish calendar. It's a 25-hour fastthat always falls on the 10th day of Tishri,which is usually in September on the secular calendar. In fact, many secular calendars now have Yom Kippurmarked. But be aware that this holy day,like the Sabbath, begins on the night before the calendar date! Why? Because in Genesis it says "there was evening and there was morning..." "Evening" is mentioned first, so Jewishdays begin at sundown.
Yom Kippur ends a10-day period of repentance and reflection known as the Ten Days of Repentance, the High Holy Days, or Yomim Noraim (Days of Awe), which began with Rosh Hashanah, the Jewish New Year.(Read my Guide on Rosh Hashanah.) During this ten-day period, Jews try to make amends to people they might have offended, make resolutions to change their own lives for the better, pay off old debts, and generally make amends for any wrong doings.
Traditional greeting
The traditional greeting for Yom Kippur is "May you be sealed for a good new year." On Rosh Hashanah,God opens the Book of Life, takes a look at all our deeds recorded there, and determines who shall live and who shall die in the geing year. But the decree is not finalized or "sealed" until the end of the day on Yom Kippur. This leaves room during the Ten Days of Repentance for people to make amends, change their behavior, and "avert the evil decree."
Fasting and other self-denials on this day
The biblical gemandment for Jews to observe Yom Kippuris found in Leviticus:

"The Lord spoke to Moses saying '...the tenth day of this seventh month is the Day of Atonement. It shall be a holy gathering for you, and you shall afflict your souls... You shall do not work throughout that day; for it is a day of atonement..." (Leviticus 23:26-32)
To "afflict your soul" means to fast and repent. There are five things that it is forbidden to do on Yom Kippur:


no eating or drinking