"...The Christian feast day of Pentecost is seven weeks after Easter Sunday: that is to say, the fiftieth day after Easter inclusive of Easter Sunday. It commemorates the descent of the Holy Spirit upon the Apostles and other followers of Jesus Christ while they were in Jerusalem celebrating the Feast of Weeks, as described in the Acts of the Apostles. Some Christians believe that this event represents the birth of the Church..."Wikipedia
The Pentecost is observed by most denominations of the Christian Church, including the Roman Catholics, Protestants, Eastern Orthodox, Oriental Orthodox, Eastern Catholics, Old Catholics, Anglicans plus other Christian groups as well.
Whilst this depiction by Ghiberti is truly stunning, perhaps the finest artwork on this theme would be the mosaic that represents the Pentecost in the Cathedral Basilica of Saint Louis in the Central West End area of this city in Missouri.
The stunning background scenery displays some of Ghiberti's growing qualities with regards architectural depictions. His next series of doors, described by Michelangelo as Gates of Paradise, would take this on yet further as Lorenzo Ghiberti continued to develop, in part due to his relationships with other highly skilled artists in his own studio.