Acts is a book that contains the birth of the church it records the ascension of Jesus and the Holy Spirit coming upon believers indwelling with in them and enabling the furtherance of the gospel. This is important to the church even today because they were given different tongues that the gospel may be preached throughout the world and the gifts of wisdom, healing, decernment, and preaching. Peter also gets a vision to preach the gospel to the gentiles as well.
