Shemini Atzeret (שמיני עצרת – "the Eighth of Assembly"; Ashkenazic pron. shmini-atseres) is a Jewish holiday. It is celebrated on the 22nd day of the Hebrew month of Tishrei. In the Diaspora, an additional day is celebrated, the second day being separately referred to as Simchat Torah. In Israel, as well as in Reform and Reconstructionist Judaism, the holidays of Shemini Atzeret and Simchat Torah are combined into one and the names are used interchangeably.
Read more about Shemini Atzeret: Relationship To Sukkot, Observances and Customs, Observance of Shemini Atzeret in Non-rabbinical Jewish Traditions