Pentecost is the great festival that marks the birth of the Christian church by the power of the Holy Spirit. Pentecost means "fiftieth day" and is celebrated fifty days after Easter.
What happened on Pentecost?
Ten days after Jesus ascended into heaven, the twelve apostles, Jesus' mother and family, and many other of His disciples gathered together in Jerusalem for the Jewish harvest festival that was celebrated on the fiftieth day after Passover. While they were indoors praying, a sound like that of a rushing wind filled the house and tongues of fire descended and rested over each of their heads. This was the outpouring of the Holy Spirit on human flesh promised by God through the prophet Joel (Joel 2:28-29). The disciples were suddenly empowered to proclaim the gospel of the risen Christ. They went out into the streets of Jerusalem and began preaching to the crowds gathered for the festival. Not only did the disciples preach with boldness and vigor, but by a miracle of the Holy Spirit they spoke in the native languages of the people present, many who had come from all corners of the Roman Empire. This created a sensation. The apostle Peter seized the moment and addressed the crowd, preaching to them about Jesus' death and resurrection for the forgiveness of sins. The result was that about three thousand converts were baptized that day. (You can read the Biblical account of Pentecost in Acts 2:1-41).
What is the liturgical color for Pentecost?
Red is the liturgical color for this day. Red recalls the tongues of flame in which the Holy Spirit descended on the first Pentecost. The color red also reminds us of the blood of the martyrs. These are the believers of every generation who by the power of the Holy Spirit hold firm to the true faith even at the cost of their lives.
Why is Pentecost sometimes called "Whitsunday"?
A tradition of some churches in ancient times was to baptize adult converts to the faith on Pentecost. The newly baptized catechumens would wear white robes on that day, so Pentecost was often called "Whitsunday" or "White Sunday" after these white baptismal garments. Many Christian calendars, liturgies, and hymnals (particularly those from the Episcopal/Anglican tradition) still use this term.
Why is Confirmation often celebrated on Pentecost?
Confirmation Sunday is the day when young people who have been instructed in basic Christian doctrine confess their faith in the presence of the church. The key to understanding confirmation is to recognize that the faith the confirmands confess is not of their own making; it is the gift of God that He gives through His means of grace. The Holy Spirit who empowered the disciples to preach the risen Christ two thousand years ago is the same Spirit who empowers the confirmands to make their confession. This is why many churches celebrate the rite of confirmation on Pentecost.
What is the season after Pentecost?
The season after Pentecost is centered on sanctification, the work of the Holy Spirit in the day to day life of the Christian. This is reflected in the liturgical color for this season: green, the color of life and growth. Through the gift of faith that comes only from the Holy Spirit working through the means of grace, Christians trust in Christ as Savior and proclaim Him in their daily lives by service to their neighbors. The season after Pentecost is the longest season of the church year -- it lasts from Trinity Sunday until the first Sunday of Advent. This is the non-festival portion of the liturgical calendar during which the church stresses vocation, evangelism, missions, stewardship, almsgiving, and other works of mercy and charity as ways in which Christ empowers us by His grace to share the Gospel with others.
Why do we celebrate Pentecost?
There are three "mega-festivals" commemorated in the Christian calendar. The first two, Christmas and Easter, are well known to both believers and non-believers. But it's possible that even liturgical Christians may not be as familiar with the third, the festival of Pentecost. God the Father's wonderful Christmas gift of His one and only Son, and Christ's Easter triumph over the power of sin, death, and the devil would be of no benefit to us if the Holy Spirit did not give us the gift of saving faith. Through the Word and Sacraments, the Holy Spirit gives us the faith which believes and trusts in Christ as our Savior. This precious gift of faith in the saving work of our Lord Jesus Christ is the reason Pentecost is the third "mega-festival" of the church and why we celebrate it with such joy and thanksgiving.
(Adapted from http://www.stpaulskingsville.org/pentecost.htm)