Sukkot is a weeklong Jewish holiday that comes five days after Yom Kippur. Sukkot celebrates the gathering of the harvest and commemorates the miraculous protection G‑d provided for the children of Israel when they left Egypt. We celebrate Sukkot by dwelling in a foliage-covered booth (known as a sukkah) and by taking the “Four Kinds” (arba minim), four special species of vegetation.
The first two days (sundown on October 13 until nightfall on October 15 in 2019) of the holiday (one day in Israel) are yom tov, when work is forbidden, candles are lit in the evening, and festive meals are preceded by Kiddush and include challah dipped in honey.
The intermediate days (nightfall on October 15 until sundown on October 20 in 2019) are quasi holidays, known as Chol Hamoed. We dwell in the sukkah and take the Four Kinds every day of Sukkot (except for Shabbat, when we do not take the Four Kinds).
The final two days (sundown on October 20 until nightfall on October 22 in 2019) are a separate holiday (one day in Israel): Shemini Atzeret / Simchat Torah.
Of all the Jewish holidays, Sukkot is the only one whose date does not seem to commemorate a historic event. The Torah refers to it by two names: Chag HaAsif (“the Festival of Ingathering,” or “Harvest Festival”) and Chag HaSukkot (“Festival of Booths”), each expressing a reason for the holiday.
In Israel, crops grow in the winter and are ready for harvest in the late spring. Some of them remain out in the field to dry for a few months and are only ready for harvest in the early fall. Chag HaAsif is a time to express appreciation for this bounty.
Taking of the Four Kinds: an etrog (citron), a lulav (palm frond), three hadassim (myrtle twigs) and two aravot (willow twigs).
On each day of the festival (except Shabbat), we take the Four Kinds, recite a blessing over them, bring them together and wave them in all six directions: right, left, forward, up, down and backward. The sages of the Midrash tell us that the Four Kinds represent the various personalities that comprise the community of Israel, whose intrinsic unity we emphasize on Sukkot.
Source: Chabad