Gaudete Sunday is so named from the Latin word for "Joy", which is also the first word of the Entrance Antiphon for the Third Sunday of Advent:
Rejoice in the Lord always; again I say, rejoice. Indeed, the Lord is near.- Philippians 4:4-5 Gaudete in Domino semper: iterum dico, gaudete.
Gaudete Sunday is one of the two days in the liturgical year where priests and deacons traditionally wear rose-colored vestments. The other day is Laetare Sunday, the Third Sunday of Lent.
The rose color reflected in the vestments of the priest provide a visual reference to the change in the emphasis of the liturgy. During the first two weeks of Advent, the priest's purple vestments reflect a restrained theme emphasizing the Lord who is to come. Gaudete Sunday begins the joyful anticipation on the Lord who is close at hand, which is the mystery of the incarnation.
The uniqueness of Gaudete Sunday in Advent, as Laetare Sunday in Lent, seems to mark a halfway point in the liturgical season. Advent gives us encouragement to persevere with our spiritual preparations for the Christmas season and beyond.
The Season of Christmas extends beyond the celebration of the Solemnity of the Nativity of Our Lord on December 25th. The Season of Christmas continues and is celebrated in the Church through the Feast of the Baptism of the Lord every year.