The Four Species are four different kinds of plants that have symbolic significance during the Jewish holiday of Sukkot. In Leviticus 23:40, which comes directly after a discussion of Sukkot, the Torah tells us: "On the first day you shall take the product of hadar trees, branches of palm trees, boughs of leafy trees, and willows of the brook, and you shall rejoice before Adonai your God seven days." From this text emerged the Four Species: a citron, a palm branch, three myrtle twigs and two willow branches.
During Sukkot the four species are brought together in the form of an etrog and the lulav. The etrog is a kind of citron, while the lulav is a composed of three myrtle twigs (hadassim), two willow twigs (aravot) and a palm frond (lulav). Because the palm frond is the largest of these plants, the myrtle and willow are wrapped around it.
The Four Species are waved together along with special blessings as part of the synagogue service during Sukkot. They can also be waved at home or near the sukkah. Traditionally the Four Species are not waved on Shabbat because doing so would violate the prohibition against carrying things during the sabbath.