We tend to think of Advent only as the season in which we prepare for Christmas, or the First Coming of Christ, but as the General Norms point out, it is important that we also remember it as a celebration in which we look forward to the Second Coming of Christ.  

The act of lighting the candles banishes the darkness: a reminder of Jesus Christ, the Light who has come into the world through his birth, and who continues to shine brightly through his Church.