Advent is a period of preparation, extending over four Sundays, before Christmas.

The word Advent comes from the Latin advenio, “to come to,” and refers to the coming of Christ. This refers, first of all, to our celebration of Christ’s birth at Christmas; but second, to the coming of Christ in our lives through grace and the Sacrament of Holy Communion; and finally, to His Second Coming at the end of time.

The signs and symbols of Advent are explained by BustedHalo in 2 minutes.

http://https://youtu.be/S02KOlw7dlA