The Advent wreath is part of our long-standing Catholic tradition. However, the actual origins are uncertain. There is evidence of pre-Christian Germanic peoples using wreathes with lit candles during the cold and dark December days as a sign of hope in the future warm and extended-sunlight days of Spring. In Scandinavia during Winter, lighted candles were placed around a wheel, and prayers were offered to the god of light to turn "the wheel of the earth" back toward the sun to lengthen the days and restore warmth.
By the Middle Ages, the Christians adapted this tradition and used Advent wreathes as part of their spiritual preparation for Christmas.
The four candles represent the four weeks of Advent. A tradition is that each week represents one thousand years, to sum to the 4,000 years from Adam and Eve until the birth of the Savior.
Three candles are purple and one is rose. The purple candles in particular symbolize the prayer, penance, and preparatory sacrifices and good works undertaken at this time. The rose candle is lit on the third Sunday of rejoicing, because the faithful have arrived at the midpoint of Advent. The progressive lighting of the candles symbolizes the expectation and hope surrounding our Lord's first coming into the world and the anticipation of His second coming to judge the living and the dead.
The light again signifies Christ, the Light of the world.