From the Sukkot Wikipedia page:
Sukkot or Succot, in traditional Ashkenazi pronunciation Sukkos or Succos, literally Feast of Booths, is commonly translated to English as Feast of Tabernacles, sometimes also as Feast of the Ingathering. It is a biblical Jewish holiday celebrated on the 15th day of the month of Tishrei (varies from late September to late October). During the existence of the Jerusalem Temple it was one of the Three Pilgrimage Festivals (Hebrew: שלושה רגלים, shlosha regalim) on which the Israelites were commanded to perform a pilgrimage to the Temple.
Sukkot has a double significance. The one mentioned in the Book of Exodus is agricultural in nature – "Feast of Ingathering at the year's end" (Exodus 34:22) – and marks the end of the harvest time and thus of the agricultural year in the Land of Israel. The more elaborate religious significance from the Book of Leviticus is that of commemorating the Exodus and the dependence of the People of Israel on the will of God (Leviticus 23:42-43).
The holiday lasts seven days in Israel and eight in the diaspora. The first day (and second day in the diaspora) is a Shabbat-like holiday when work is forbidden, followed by intermediate days called Chol Hamoed. The festival is closed with another Shabbat-like holiday called Shemini Atzeret (two days in the diaspora, where the second day is called Simchat Torah).
The Hebrew word sukkōt is the plural of sukkah, "booth" or "tabernacle", which is a walled structure covered with s'chach (plant material such as overgrowth or palm leaves). A sukkah is the name of the temporary dwelling in which farmers would live during harvesting, a fact connecting to the agricultural significance of the holiday stressed by the Book of Exodus. As stated in Leviticus, it is also intended as a reminiscence of the type of fragile dwellings in which the Israelites dwelt during their 40 years of travel in the desert after the Exodus from slavery in Egypt. Throughout the holiday, meals are eaten inside the sukkah and many people sleep there as well.
On each day of the holiday it is mandatory to perform a waving ceremony with the Four Species.