What is Yom Kippur?

Yom Kippur (literally "Day of Atonement") is the holiest and most solemn day of the Jewish year—a day marked by communal and personal prayer, introspection, and fasting. A central tenet of Judaism is the belief that God created humanity in the image of the divine, and that as such, all beings are capable of and obligated to achieve atonement (teshuvah) for sins committed against God, against others, and against oneself. Yom Kippur offers a singular opportunity to atone for sins committed in the past year—and by extension, to reconcile with God, rectify relationships with others, and achieve personal redemption.
The fast of Yom Kippur begins at sundown and concludes at sundown the following day. Jewish tradition places great emphasis on the act of fasting, likening it to a spiritual "cleansing" meant to purify the body, mind, and soul.
The day of fasting is spent not only in solemn prayer, but in communal prayer. This act of worshipping alongside one's community serves to remind the individual that the Day of Atonement is not simply about personal atonement, but about aligning oneself with the greater spiritual body of the people of Israel. The prayers and observances of Yom Kippur are meant to unite the Jewish people, and to strengthen their covenant with God.
The Yom Kippur fast is ended at sundown, with the conclusion of the Ne'ilah service. As the sun sets and the day of fasting concludes, Jews light candles to celebrate the advent of the new year, and the forgiveness that the High Holy Days made possible.
All the best to you during this most holy time.