Acts 1

Acts is named after the "acts" the disciples performed i.e...the "acts" of the disciples.

After His resurrection Jesus appeared to the disciples over a period of 40 days (vs 3). One day Jesus gave the disciples this command: "Do not leave Jerusalem, but wait for the gift my Father promised, which you have heard me speak about. For John baptized with water, but in a few days you will be baptized with the Holy Spirit." Jesus said to the disciples after they questioned Him about restoring the kingdom to Israel, "You will receive power when the Holy Spirit comes on you; and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth." After that, Jesus was taken up into heaven.

Then the disciples returned to Jerusalem from the hill called the Mount of Olives. When they arrived, they (Peter, John, James, Andrew, Philip, Thomas, Bartholomew, Matthew, and James, some women and Mary, the mother of Jesus and his brothers all joined together constantly in prayer.

On one day, Peter stood up in front of the group which numbered 120 and said that Judas had to be replaced. It was necessary to choose someone who had been with them the whole time the Lord Jesus went and out among them to become a witness of His resurrection.

So they proposed two men: Joseph called Barsabbas and Matthias. Then they prayed, "Lord, you know everyone's heart. Show us which of these two you have chosen to take over this apostolic minstry, which Judas has left. Then they cast lots and the lot fell to Mathias; so he was added to the 11 apostles.