Page "Jewish holiday" Paragraph 61

Along with dwelling in a sukkah, the principal ritual unique to this holiday is use of the Four Species ( lulav ( palm ), hadass ( myrtle ), aravah ( willow ) and etrog ( citron ).

On each day of the holiday other than Shabbat, these are waved in association with the recitation of Hallel in the synagogue, then walked in a procession around the synagogue called the Hoshanot.