Advent comes from the Latin word meaning "coming." Jesus is coming, and Advent is intended to be a season of preparation for His arrival. While we typically regard Advent as a joyous season, it is also intended to be a period of preparation, much like Lent.
Prayer, penance and fasting are appropriate during this season.
Advent is not as strict as Lent, and there are no rules for fasting, but it is meant to be a period of self-preparation. The purple color associated with Advent is also the color of penance. The faithful should fast during the first two weeks in particular and receive the Sacrament of Reconciliation.
The color of the Third Sunday of Advent is rose. This color symbolizes joy and represents the happiness we will experience when Jesus comes again. The Third Sunday is a day of anticipatory celebration. It is formerly called "Gaudete" Sunday; gaudete means "rejoice" in Latin.
Finally, Sundays during Advent, just as during Lent, should not be given to fasting, but instead to celebration because we celebrate the resurrection of Our Lord every Sunday. It is important to remember, however, there are no particular rules for how the laity should observe Advent.