From the Directory on Popular Piety and the Liturgy, paragraphs 96-97:
Advent is a time of waiting, conversion and of hope:
· waiting-memory of the first, humble coming of the Lord in our mortal flesh; waiting-supplication for his final, glorious coming as Lord of History and universal Judge;
· conversion, to which the Liturgy at this time often refers quoting the prophets, especially John the Baptist, "Repent for the kingdom of heaven is at hand" (Mt 3,2);
· joyful hope that the salvation already accomplished by Christ (cf. Rm 8, 24-25) and the reality of grace in the world, will mature and reach their fulness, thereby granting us what is promised by faith, and "we shall become like him for we shall see him as he really is" (John 3,2).
Popular piety is particularly sensitive to Advent, especially when seen as the memory of the preparation for the coming of the Messiah. The Christian people are deeply conscious of the long period of expectation that preceded the birth of our Saviour. The faithful know that God sustained Israel's hope in the coming of the Messiah by the prophets.
Popular piety is not unaware of this extraordinary event. Indeed, it is awestruck at the prospect of the God of glory taking flesh in the womb of the humble and lowly Virgin Mary. The faithful are particularly sensitive to the difficulties faced by the Virgin Mary during her pregnancy, and are deeply moved by the fact that there was no room at the inn for Joseph and Mary, just as she was about to give birth to the Christ child (cf Lk 2,7).
Various expressions of popular piety connected with Advent have emerged throughout the centuries. These have sustained the faith of the people, and from one generation to the next, they have conserved many valuable aspects of the liturgical season of Advent.
From the General Norms for the Liturgical Year and the Calendar, 39 – 41:
Advent has a twofold character: as a season to prepare for Christmas when Christ's first coming to us is remembered; as a season when that remembrance directs the mind and heart to await Christ's Second Coming at the end of time. Advent is thus a period for devout and joyful expectation.
Advent begins with Evening Prayer I of the Sunday falling on or closest to 30 November and ends before Evening Prayer I of Christmas.[R8]
The Sundays of this season are named the First, Second, Third, and Fourth Sundays of Advent.
The weekdays from 17 December to 24 December inclusive serve to prepare more directly for the Lord's birth.