The High Holidays
The High Holiday period begins with the celebration of the Jewish New Year, Rosh Hashanah. It's important to note that the holiday doesn't actually fall on the first day of the first month of the Jewish calendar. Jews actually observe several New Year celebrations throughout the year. Rosh Hashanah begins with the first day of the seventh month, Tishri. According to the Talmud, it was on this day that God created mankind. As such, Rosh Hashanah commemorates the creation of the human race.
The High Holidays are a time for introspection and prayer.
Rosh Hashanah is often referred to as the Day of Judgement. One of the most prominent themes of the High Holiday period revolves around the symbolic "Book of Life." On Rosh Hashanah, Jews often say to one another, "May you be inscribed and sealed in the Book of Life." Being inscribed in the "Book of Life" brings with it the promise of a good new year. The belief is that on Rosh Hashanah, the names are written in the book and 10 days later, on Yom Kippur, the book is sealed. These 10 days are referred to as the Days of Awe.
The Jewish Calendar
The calendar used by most of the world is the Gregorian calendar, introduced in 1582 by Pope Gregory XIII. The Jewish calendar, which is the official calendar in Israel and the religious calendar for Jews everywhere, was instituted by Hillel II around the year 359. Whereas the Gregorian calendar is based on the sun, the Jewish calendar is based on both the sun and the moon. Years coincide with the sun, and months coincide with the moon.
For more information, see Judaism 101: Jewish Calendar and Calendars Through the Ages: The Jewish calendar.
The Days of Awe are a time of spiritual, emotional and physical cleansing. Jews are meant to reflect on the previous year, pondering their thoughts and actions and asking forgiveness for any transgressions they may have committed throughout the year. Because it is a time for introspective thought and prayer, many Jews abstain from entertainment and other pleasures during this time. Although this can be a solemn and somber period, it is also a time to rejoice in life and find hope for the coming new year. The Days of Awe and the High Holiday period give Jews the opportunity to put the sins of the previous year in the past, and move forward having received God's forgiveness.