Advent is a time of waiting, hoping, and getting in touch with our need for a Savior. It's a season of preparation for Christmas, much as Lent is a season of preparation for Easter.
In Advent we look back to the experience of Israelites as they yearned for God to forgive their sin and restore their nation. We put ourselves in their shoes as they hoped for the coming of the Messiah. Thus we ready our hearts to celebrate the good news of Christmas.
Yet Advent is also a time to look forward to the second coming of Christ. Though defeating sin and death through His cross and resurrection, Christ hasn't yet finished His work of renewing creation and restoring the kingdom of God. Thus we continue to experience the brokenness of this world, in violence, disease, natural disasters, and other forms of human suffering. In Advent we yearn for God's completion of the salvation begun in Christ. --Mark Roberts