Shavu’ot (Hebrew: שָׁבוּעוֹת ) the Festival of Weeks, is the second of the three major festivals with both historical and agricultural significance.
Agriculturally, it commemorates the time when the first fruits were harvested and brought to the Temple and is known as Hag ha-Bikkurim (the Festival of the First Fruits). Historically, it celebrates the giving of the Torah at Mount Sinai and is also known as Hag Matan Torateinu (the Festival of the Giving of Our Torah).
The period from Passover to Shavuot is a time of great anticipation. We count each of the days from the second day of Passover to the day before Shavuot, 49 days or 7 full weeks, hence the name of the festival. Shavuot is also sometimes known as Pentecost because it falls on the 50th day. The counting reminds us of the important connection between Passover and Shavuot: Passover freed us physically from bondage, but the giving of the Torah on Shavuot redeemed us spiritually from our bondage to idolatry and immorality.
In the Bible, Shavuot is called the Festival of Weeks (Exodus 34:22, Deuteronomy 16:10) or festival of Reaping (Exodus 23:16) and Day of the First Fruits (Numbers 28:26). The Mishnah and Talmud refer to Shavuot as Atzeret (a solemn assembly), as it provides closure for the festival activities during and following the holiday of Passover.