During Temple times, Sukkot was one of the three pilgrimage feasts in which the children of Israel would travel up to the Temple in Jerusalem to present themselves before the Lord and make sacrifices.
In Leviticus 23, the Lord commanded the children of Israel to build booths and dwell in them throughout the week of Sukkot. This was to remember how the Lord sustained and provided for them when they lived in tents after He led them out of Egypt.
According to the Talmud, it is important to be able to see the night stars directly through the top of the sukkah. This is why sukkot booths today never have a closed roof, but rather branches of bamboo, pine or natural foliage with gaps in between. The Feast of Tabernacles is all about hospitality and fellowship. It is traditional to eat in the Sukkah and invite others to share in the joyous celebration.
Many people don't realize that Sukkot has two different names in the Bible. In Exodus 34:22, it is called 'The Feast of Ingathering at the year's end.' This refers to the harvest that was brought in after the summer (some of the harvest was gathered before the summer during the Feast of Shavuot). These two names—the Feast of Tabernacles and the Feast of Ingathering—celebrate two different aspects of G-d's faithful provision: the provision of shelter and the provision of the harvest.
All in all, Sukkot is a fun and joyous holiday, with a focus on spending quality time with friends and family and celebrating the goodness of the Lord.