HOLY DAY OF OBLIGATION
The Ascension is the event, where Jesus arose into heaven, at the end of his time on earth.
Jesus' time on earth began with his birth. It was interrupted for three days by His death on the Cross. During that time, He descended into the realm of the dead and preached the Gospel to the good people who died before Him. This allowed those good and holy souls--the righteous dead, as we call them--who accepted Christ as their Savior to proceed to heaven. On the third day after his death and burial, Jesus Christ was raised from the dead, an event we call the Resurrection. He spent the next 40 days preaching and preparing His disciples to perform the work of preaching and baptizing all people.
At the end of this 40 day period, Jesus ascended into heaven. We call this the Ascension.