The Dictionary describes the Holy Spirit as, "the spirit of God"
The Spirit of God is seen all throughout the Hebrew Bible, beginning in the second verse of Genesis. "Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters." The Spirit of God features prominently in Judges, 1st/2nd Samuel, and 1st/2nd Kings. David refers to Him in Psalm 51:11, "Do not cast me from your presence or take your Holy Spirit from me." The Holy Spirit appears even more prominently in the New Testament. Jesus talked about Him often. The Holy Spirit is part of the Trinity - God the Father, God the Son (Jesus), and God the (Holy) Spirit. (Matthew 28:19) The Holy Spirit plays a large role in the book of Acts, which was written by Dr. Luke. In fact, the Holy Spirit is first mentioned in the second verse of Acts. "until the day [Jesus] was taken up to heaven, after giving instructions through the Holy Spirit to the apostles He had chosen." Despite what some traditions may say, I would contend that the Holy Spirit is alive and active - He is a being. He speaks (Acts 1:16; 8:29; 10:19; etc.), He enables people to speak, in some occasions different languages (Acts 2:4; 4:8, 31), He bears witness to things (Acts 5:32), He sends out Christians (Acts 13:4), the Holy Spirit "has made... overseers," in other words, appointing people to accomplish tasks, He also is equal to God the Father and is linked with us. (Acts 5:3, 9; 15:28) (Photo credit to: TurnBackToGod)
Acts 16:7 also calls Him the "Spirit of Jesus" (see Romans 8:9). This further links the Holy Spirit with God the Father, since Jesus is God the Son. Since we know that the Holy Spirit is God the Spirit, this is perfectly logical. How did the Holy Spirit work in Acts? We begin in Acts 2:2-4. "Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. They saw what seemed to be tongues of fire that separated and came to rest on each of them. All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them."
It can be noted that Dr. Luke illustrates in Acts the progression of the gospel as well as the expansion of the church through the Holy Spirit. The church began with Jews and Gentiles who were committed to Judaism as if they were Jews, but the Holy Spirit expanded this to all people, including Samaritans (Acts 8:14-17). The Holy Spirit enables us, both men and women, to be a witness. (Acts 1:8; 4:33) By being filled with the Holy Spirit, we can speak with power. (Acts 2:4, 14; 4:8, 31; 6:10) Acts 8:29 says, "The Spirit told Philip, 'Go to that chariot and stay near it." Acts 10:19 reveals, "While Peter was still thinking about the vision, the Spirit said to him, 'Simon, three men are looking for you.'" These two verses reveal that the Holy Spirit has on occasion told Christians to preach to certain men, but does not reveal the manner in which this is revealed. (Speech/Thought)
Just as the Holy Spirit was involved in prophecy all throughout the Hebrew Bible, He was (and still is) involved in the New Testament. He prophesied through Agabus (Acts 21:10-11), which was fulfilled when St. Paul was imprisoned by Gentiles. Prophecy was connected to the church in the way that it strengthened and encouraged the church. (Acts 15:32) Compare this to 1st Corinthians 14:3 which says, "But to those who prophesy speak to people for their strengthening, encouragement and comfort." The Holy Spirit's activities are clearly seen in Acts and continue today. This is to fulfill what was said through the prophet Joel, "And afterward, I will pour out my Spirit on all people. Your sons and daughters will prophesy, your old men will dream dreams, your young men will see visions. Even on my servants, both men and women, I will pour out my Spirit in those days." (Joel 2:28-29)
This also occurred to fulfill what Jesus said while on earth. John 14:16-17, "And I will ask the Father, and he will give you another advocate to help you and be with you forever - the Spirit of truth. The world cannot accept him, because it neither sees him nor knows him. But you know him, for he lives with you and will be in you." He also says in Luke 15:26, "When the Advocate comes, whom I will send to you from the Father - the Spirit of truth who goes out from the Father - he will testify about me." The Holy Spirit plays a prominent role in the lives of every person on the planet, whether they realize it or not. The Holy Spirit is the one whom we ought to credit with the expansion and spread of Christianity. No single man has influenced history as much as Jesus Christ (see entry: "Jesus: The Most Influential Person In History?"), and God the Spirit has been and is the cause for this. We all experience the effects that Jesus has had on all areas of life: history, politics, economics, social areas, etc. This has all been furthered by the Holy Spirit through people.
The Holy Spirit plays an important role in Acts, and all throughout History. God the Spirit was there In the Beginning: God spoke, and the Spirit acted. The Holy Spirit literally wrote each book of the Bible using over 40 individual authors, though He allowed them to bring their research and knowledge to the books, but corrected them where they were wrong. (2nd Timothy 3:16, 2nd Peter 1:20-21) As pointed out in 2nd Peter 21, "For prophecy never had its origin in the human will, but prophets, though human, spoke from God as they were carried along through the Holy Spirit." Acts 2:29-33 reveals to us that indeed the Holy Spirit truly did write through people, such as King David. In the book of Acts, the Holy Spirit is directly responsible for the miracles, healings, and raising the dead to life. The Holy Spirit worked through St. Peter, St. Paul, Dr. Luke, St. John, and many, many others. St. Peter healed a lame beggar (Acts 3:1-10), the apostles healed many people (Acts 5:12-16), allowed St. Paul to raise to life a dead youth (Acts 20:7-12), and many other acts.