Today, the First Sunday of Advent, begins the new Liturgical Year and the season of Advent. The word advent in latin means "coming". So, Advent is the preparation time for the coming of the Lord at Christmas. Although Christ came, historically, two thousand years ago, He come again to us, mystically, at Christmas. And He will come again in the Second Coming where He will judge the living and the dead.
Advent is a time of joy and hope, tinged with a touch of penance so that we may be spiritually prepared to receive Him at Christmas. This is all symbolized in the Advent wreath whereby we have the four candles (one for each Sunday). The evergreens symbolize life in the midst of winter; the candles symbolize the light of Christ in the darkness (the pink one for the 3rd Sunday represents joy); and the purple (color of the season) represents the penitential flavor of the season.