The Passover Feast commemorates Israel’s deliverance from slavery in Egypt. Jews also celebrate the birth of the Jewish nation after being freed by God from captivity. Today, the Jewish people not only celebrate Passover as a historical event but in a broader sense, celebrate their freedom as Jews.

The Hebrew word Pesach means “to pass over.” During Passover, Jews take part in the Seder meal, which incorporates the retelling of Exodus and God’s deliverance from bondage in Egypt. Each participant of the Seder experiences in a personal way, a national celebration of freedom through God’s intervention and deliverance.

Hag HaMatzah (the Feast of Unleavened Bread) and Yom HaBikkurim (Firstfruits) are both mentioned in Leviticus 23 as separate feasts. However, today Jews celebrate all three feasts as part of the eight-day Passover holiday.

Passover begins on day 15 of the Hebrew month of Nissan (March or April) and continues for eight days. Initially, Passover began at twilight on the fourteenth day of Nissan (Leviticus 23:5), and then on day 15, the Feast of Unleavened Bread would begin and continue for seven days (Leviticus 23:6).

Source: https://www.thoughtco.com/bible-feast-of-passover-700185

The Feast of Pentecost or Shavuot has many names in the Bible: The Feast of Weeks, the Feast of Harvest, and the Latter Firstfruits. Celebrated on the fiftieth day after Passover, Shavuot is traditionally a joyous time of giving thanks and presenting offerings for the new grain of the summer wheat harvest in Israel.

The name “Feast of Weeks” was given because God commanded the Jews in Leviticus 23:15-16, to count seven full weeks (or 49 days) beginning on the second day of Passover, and then present offerings of new grain to the Lord as a lasting ordinance. The term Pentecost derives from the Greek word meaning “fifty.”

Initially, Shavuot was a festival for expressing thankfulness to the Lord for the blessing of the harvest. And because it occurred at the conclusion of the Passover, it acquired the name “Latter Firstfruits.” The celebration is also tied to the giving of the Ten Commandments and thus bears the name Matin Torah or “giving of the Law.” Jews believe that it was precisely at this time that God gave the Torah to the people through Moses on Mount Sinai.

Source: https://www.thoughtco.com/feast-of-pentecost-700186