The 23rd is the last Sunday of Advent, a period of fasting, reflection, and preparation for the Christmas holidays.
On this Sunday the fourth candle in the Advent Wreath (or Crown) is lighted, symbolizing Love. (The first three stand for Hope, Peace, and Joy.) If there is a fifth candle- the Christ candle, it is lighted at the Christmas Eve service.
Aside from the Advent Wreath, there are other traditions some Christians enjoy during advent. Some decorate a Jesse Tree with symbols of the ancestors of Christ (on his human side). Like the advent wreath, this seems to have been a teaching tool. David, was the ancestor most often mentioned, Jesse was his father, Mary and Joseph, Abraham, Moses and Noah may also be represented.