Shavuot ("weeks") is one of three Pilgrim Festivals (along with Passover and Sukkot) in the Jewish calendar. It falls on the sixth day of Sivan beginning at sunset the night before and celebrates the Ten Commandments, the foundation of Jewish law. Shavuot is also known as the Feast of Weeks because it occurs seven weeks after the first day of Passover.
Originally, Shavuot was a time of bringing the first fruits of harvest to Jerusalem as a show of thanks but has since transformed into the anniversary of the day the Torah was given to the Jewish people.
It is customary to read from the Book of Ruth and study the Torah during Shavuot.