Acts 1:8 (NKJV)
But you will receive power when the Holy Spirit has come upon you; and you shall be witnesses to Me in Jerusalem, and in all Judea and Samaria, and to the end of the earth.
The Holy Spirit is Christ in the Christian. While Jesus was here with us, he could not be in everyone of us. That is why He said that it was good that He goes away, so that the Holy Spirit (really the Spirit of Himself), could come to abide in every one of us.
Like any good CEO, Jesus makes sure we are equipped with plenty of Power. Then Jesus lays out the plan for us, three concentric circles. We begin in our own familiar neighborhood, then we move out into the surrounding regions, and finally we encompass the entire world. What is the task? We are to be witnesses of Him, telling people about Jesus and what we have seen and heard and know that He has done in our own life.