Pentecost is a Christian festival. The sending of the Holy Spirit is celebrated by the faithful. It is celebrated on the fiftieth day after Easter. Pentecost is also known as the "Outpouring of the Holy Spirit". Pentecost commemorates the descent of the Holy Spirit upon the Twelve apostles and other followers of Jesus as described in the Acts of the Apostles 2:1-31. Therefor Pentecost is described as the "Birthday of the Church."