What does Acts 1:1 mean?
The Acts of the Apostles is Luke's second book to Theophilus, the first being the Gospel of Luke. We don't know exactly who Theophilus is. In Luke 1:3, Luke gives him the title "most excellent," from krastistos in Greek, suggesting he is in the Roman military's equestrian corps. It is from this unit that the procurators of Judea were typically taken (Acts 24:2; 26:25). "Theophilus" means "lover of God." Luke may be using a pseudonym to hide the identity of a Christ-follower who holds high rank in the local government. By the time of Luke's writing—after Paul's first imprisonment (Acts 28:30)—Roman persecution of Christianity is heating up and a government official would not be immune from danger (Acts 28:22).We know more about Luke than we do Theophilus. Paul calls him a "beloved physician" (Colossians 4:14). Paul also records that Luke is in Rome during Paul's first (Colossians 4:10, 14) and second (2 Timothy 4:11) imprisonments. Tradition says that Luke is from Syrian Antioch, the headquarters of Paul and Barnabas, and that he is Semitic but Gentile. Scholars examining Luke's writing note that he is educated in Greek rhetoric as well as Jewish history and Scripture. Having followed Paul for years, he would have no choice but to be well-versed in Jesus' native culture.
The Gospel of Luke covers the life and teaching of Jesus. Luke has ample time during Paul's imprisonment in Caesarea Maritima (Acts 24—26) to interview the apostles for details of Jesus' ministry. But tradition suggests Luke relies on another, unique, source. The genealogy given in Matthew 1:1–16 differs from that in Luke 3:23–38, splitting at King David's sons. Scholars believe Luke gives Mary's genealogy whereas Matthew traces Jesus' lineage through Joseph. Luke also includes details such as Jesus' birth and early childhood, the birth of His cousin John (Luke 1:5–25), John's recognition of Jesus while both are still in the womb (Luke 1:39–45), and Mary's song of praise (Luke 1:46–56). Taken together, it's very possible Luke received much of his information from Mary, herself.
There is no indication that Luke ever met Jesus personally. He did know Paul, however, as well as the leaders of the church in Jerusalem (Acts 21:17–18). What events he does not witness personally, he is in position to easily receive accounts from those who did.