Answer:
It's the four weeks prior to Christmas.
It symbolises two things - a period of time when we wait for Christ to appear on earth at Christmas, and a period of time when we think of his second coming at some stage in the future.
Advent is marked by a period of prayerful self-exaination for the Christian and, though not as sombre a season as Lent, it is still nevertheless a period of time that is more reflective and a time when Christians should examine their lives and strive to reflect God's love as shown at the coming of Jesus.