The candles symbolize the coming of Christ, and traditionally, one is lit the first Sunday before Christmas and the two Sundays following. The fourth candle is lit either on Christmas Eve or on Christmas Day.
The Lutheran Church Missouri Synod’s Church-Year document explains that three purple candles represent the royalty of Christ, and a pink candle – lit on the third Sunday in Advent, represents the joy of His coming.
The United Methodist Church celebrates on each Sunday in Advent one of the four virtues of Christ: Hope, Love, Joy and Peace. Some churches use four purple candles for the four weeks of Advent, and a fifth white candle in the center – the “Christ candle.”
The Catholic Education Resource Center (CERG) website offers a history of Advent as well, noting the evergreen wreath symbolizes continuous life, and the candles represent the light, which is Christ.