The twelve apostles and Mary were in the upper room together praying.
Tongues of fire rested on each of them. They were filled with the Holy Spirit.
The people thought Peter and the apostles were drunk because of what they were saying. Peter responded quoting the book Joel in the Old Testament. The book Joel said about how in the last days God will pour out his Spirit on all people.
Peter proclaimed to the people gathered in their native tongue that Jesus was both God and Christ.
Peter told the people to repent and to be baptized, so that they may receive the Holy Spirit.
"Each of you must repent for your sins and turn to God, and be baptized in the name of Jesus Christ for the forgiveness of your sins. Then you will receive the gift of the Holy Spirit."
About 3,000 people were baptized on Pentecost.
Because the Holy Spirit enabled the apostles to speak different languages, they were able to spread the Word of God. The people that were baptized on Pentecost were then able to spread the Word of God to others. Now, the Church has millions of followers around the world.