S’lichot, a Hebrew word meaning “forgiveness,” refers to the special penitential prayers recited by Jews throughout the High Holy Days. Jews recite S’lichot beginning late at night on the Saturday before Rosh HaShanah and continue each morning on the days between the New Year and Yom Kippur.
Rosh HaShanah (literally, “Head of the Year”) is the celebration of the Jewish New Year, observed on the first day of the Hebrew month of Tishrei. It marks the beginning of a ten-day period of prayer, self-examination and repentance, culminating on the fast day of Yom Kippur. These ten days are referred to as Yamim Noraim, the Days of Awe or the High Holy Days.
While there are elements of joy and celebration, Rosh HaShanah is a deeply religious occasion. The customs and symbols of Rosh HaShanah reflect the holiday’s dual emphasis, happiness and humility. Special customs observed on Rosh HaShanah include; the sounding of the shofar, using round challah, eating apples and honey (and other sweet foods) for a sweet new year.
There is also a customary service observed before Rosh HaShanah. S’lichot, meaning forgiveness, refers to the solemn penitential prayers recited by Jews prior to the onset of the High Holy Days.
Yom Kippur is the “Day of Atonement” and refers to the annual Jewish observance of fasting, prayer and repentance. This is considered to be the holiest day in the Jewish calendar. In three separate passages in the Torah, the Jewish people are told, “the tenth day of the seventh month is the Day of Atonement. It shall be a sacred occasion for you: You shall practice self-denial.”(Leviticus 23:27). Fasting is seen as fulfilling this biblical commandment. The Yom Kippur fast also enables us to put aside our physical desires and to concentrate on our spiritual needs through prayer, repentance and self-improvement. It is customary in the days before Yom Kippur for Jews to seek out friends and family whom they have wronged and personally ask for their forgiveness.
The above content and additional information can be found at https://urj.org/holidays/highholidays/.