A long time member of our church confessed the other day that she didn't really understand Pentecost. As Pentecost is not celebrated outside of the church - we don't give Pentecost cards, or get days off from work or school - this is not surprising. Here is a primer for her and others who might be wondering.
Pentecost literally means "fiftieth" and one of the three major feast days in ancient Judaism marking the fiftieth day following Passover. In Acts chapter 2, we learn that the disciples were all gathered together on that day when a "sound like the rush of a violent wind" filled the house and "tongues as of fire rested on each of them. All were filled with the Holy Spirit." The Holy Spirit empowers the disciples, who until then had been passive to say the least, to rush out into the crowded city and talk about Jesus. Miraculously, when they talk, everyone can understand regardless of their native language. Peter preaches what is perhaps the greatest sermon ever and over 1,000 people are converted.
Christians consider Pentecost to be the birthday of the church and along with Easter and Christmas is one of the most important liturgical holidays.
In some Christian traditions, churches are decorated in red for Pentecost. Somebody back in the Middle Ages decided that the color red symbolized the Holy Spirit, and that tradition has been passed down through the churches ever since.