Jesus led them out of the city as far as Bethany, where he raised his hands and blessed them. He was then taken up into Heaven. They worshiped him and went back into Jerusalem, filled with great joy, and spent all their time in the temple giving thanks to God.
The ascension literally means that Jesus ascended, or was taken up, to Heaven. This is significant as it shows that he has returned to Heaven after completing his mission on Earth.
Christians believe that Jesus is in Heaven with God, until He decides to send Jesus to Earth for the final judgement. This event is known as the Parousia.