In the Christian tradition, Advent wreaths are as beautiful as they are symbolic. These evergreen wreaths are shaped in a perfect circle to symbolize the eternity of God. Advent wreaths have four candles that remind us that Christ is the light of the world. One of these candles is rose or pink. We light it on Gaudete Sunday, the third Sunday in Advent, to represent the joy and anticipation of Christmas.
Source: Catholic Extension