The festival of Shavuot celebrates the giving of the Torah at Mount Sinai.
Tishah B'Av is a day of mourning the destruction of both ancient Temples in Jerusalem.
For many Jews, the High Holiday season begins with Rosh HaShanah and the start of the new month of Tishrei. Jewish tradition, however, teaches that the preceding month of Elul is a time of soul-searching and reflection to prepare oneself for the magnitude of the Days of Awe. It is during this time that we observe Selichot (also spelled s'lichot).
Rosh HaShanah is the Jewish New Year, a time of prayer, self-reflection, and repentance.