Sukkot is a week long holiday that starts on the 15th day of the Hebrew month Tishrei. It commemorates the beginning of the construction of the Holy Tabernacle after the Exodus from Egypt.
Sukkot is one the three Holidays of pilgrimage to the Holy Temple in Jerusalem. In the Torah the pilgrimage holidays are mentioned three times (see below).
"On the 15th of the seventh month, when you harvest the land's grain, you shall celebrate a festival to God for seven days. The first day shall be a day of rest, and the eighth day shall be a day of rest." (Leviticus 23:39)
Sukkot is the plural form of the Hebrew word sukkah which means a tabernacle. Sukkah structure symbolizes the makeshift huts in which the Hebrews lived during their journeys in the desert after exodus from Egypt.
"On the first day, you must take for yourself a fruit of the citron tree, an unopened palm frond, myrtle branches, and willows [that grow near] the brook. You shall rejoice before God for seven days." (Leviticus 23:40)
"Celebrate three pilgrimage festivals to Me each year.
Keep the Festival of Matzahs. Eat matzahs for seven days, as I commanded you, during the prescribed time in the month of standing grain, since this is when you left Egypt.
Do not appear before Me empty-handed.
Also keep] the Reaping Festival, through the first fruits of your produce that you planted in the field. [There is also] the Harvest Festival [right after] the end of the year, when you gather your produce from the field." (Exodus 23:14-16)
Three times each year, every male among you must appear before God, Master [of the Universe]. (Exodus 23:17, 34:23)
Three times each year, all your males shall thus be seen in the presence of God your Lord in the place that He will choose: on the festival of Matzahs, on the festival of Shavuoth, and on the festival of Sukkoth. [In those times] you shall not appear before God empty-handed.
Each person shall bring his hand-delivered gift, depending on the blessing that God your Lord grants you. (Deuteronomy 16:16-17)