From Matt Jenson and David Wilhite Church: A Guide for the Perplexed (Guides For The Perplexed):
At Pentecost, Joel’s prophecy [2:28-29] is fulfilled and Babel [Genesis 11] is undone.
What Pentecost represents — and in this it marks the beginning of the mission of the church — is the unity of the gospel (‘one Lord, one faith, one baptism’ — Eph. 4.5) communicated in a diversity of languages, all in the power of the Holy Spirit. Note, too, that the unity of proclamation does not require — we might even say, does not allow for — a unified language. This signals a Spirit-directed, Spirit-filled flourishing of the many — as many — as they are united to the one Lord.
The Pentecostal gift is nothing less than empowerment for mission in which the Spirit catholicizes the people of God.
The Spirit is also the one who particularizes Christ’s person and work, uniting and conforming individuals to Christ. By applying Christ catholically and personally, the Spirit constitutes the Church.