"Pentecost Sunday, May 24, this celebration always lands on the fiftieth and final day of the Easter season, reflecting its origin from the Greek work pentēkostē, meaning 'fiftieth.' Pentecost is also closely linked with the Jewish Feast of Weeks (Shavuot), which takes place fifty days after Passover, and which celebrates the wheat harvest and the giving of the law of Mount Sinai – thus prefiguring how the Holy Spirit has equipped God’s people to proclaim and live fully Christ’s new law of grace, and fulfillment of the Old Covenant law (Mt 5:17-18).
Pentecost is a Christian celebration that commemorates the day when the Holy Spirit descended upon the followers of Jesus, 'And suddenly a sound came from Heaven like the rush of a mighty wind, and it filled all the houses where they were sitting (Acts 2:2). And 'tongues as of fire' came to rest on each of them (Acts 2:3)...
Why is Pentecost Sunday important in the Catholic Faith? For Catholics, Pentecost Sunday is not merely a historical commemoration, it’s a great liturgical celebration, memorializing the day on which Jesus sent the Holy Spirit to inaugurate and ignite the Church’s public mission, 'You shall receive power when the Holy Spirit has come upon you.' (Acts 1:8). It celebrates the day on which the Holy Spirit empowers Christ’s Church to act boldly in Jesus’ name. Liturgically, Pentecost concludes the season of Eastertide..."