History
The word “Advent” is derived from the Latin word adventus, meaning “coming,” which is a translation of the Greek word parousia. Scholars believe that during the 4th and 5th centuries in Spain and Gaul, Advent was a season of preparation for the baptism of new Christians at the January feast of Epiphany, the celebration of God’s incarnation represented by the visit of the Magi to the baby Jesus (Matthew 2:1), his baptism in the Jordan River by John the Baptist (John 1:29), and his first miracle at Cana (John 2:1). During this season of preparation, Christians would spend 40 days in penance, prayer, and fasting to prepare for this celebration; originally, there was little connection between Advent and Christmas.
By the 6th century, however, Roman Christians had tied Advent to the coming of Christ. But the “coming” they had in mind was not Christ’s first coming in the manger in Bethlehem, but his second coming in the clouds as the judge of the world. It was not until the Middle Ages that the Advent season was explicitly linked to Christ’s first coming at Christmas.
Current Practice
Today, the Advent season lasts for four Sundays leading up to Christmas. At that time, the new Christian year begins with the twelve-day celebration of Christmastide, which lasts from Christmas Eve until Epiphany on January 6. (Advent begins on the Sunday that falls between November 27th and December 3rd each year.)
Advent symbolizes the present situation of the church in these “last days” (Acts 2:17, Hebrews 1:2), as God’s people wait for the return of Christ in glory to consummate his eternal kingdom. The church is in a similar situation to Israel at the end of the Old Testament: in exile, waiting and hoping in prayerful expectation for the coming of the Messiah. Israel looked back to God’s past gracious actions on their behalf in leading them out of Egypt in the Exodus, and on this basis they called for God once again to act for them. In the same way, the church, during Advent, looks back upon Christ’s coming in celebration while at the same time looking forward in eager anticipation to the coming of Christ’s kingdom when he returns for his people. In this light, the Advent hymn “O Come, O Come, Emmanuel” perfectly represents the church’s cry during the Advent season:
O come, O come, Emmanuel,
And ransom captive Israel,
That mourns in lonely exile here
Until the Son of God appears.
Rejoice! Rejoice!
Emmanuel shall come to thee, O Israel.
While Israel would have sung the song in expectation of Christ’s first coming, the church now sings the song in commemoration of that first coming and in expectation of the second coming in the future.
Advent Liturgy and Practice
To balance the two elements of remembrance and anticipation, the first two Sundays in Advent (through December 16th) look forward to Christ’s second coming, and the last two Sundays (December 17th – 24th) look backward to remember Christ’s first coming. Over the course of the four weeks, Scripture readings move from passages about Christ’s return in judgment, to Old Testament passages about the expectation of the coming Messiah, to New Testament passages about the announcements of Christ’s arrival by John the Baptist and the Angels.
While it is difficult to keep in mind in the midst of holiday celebrations, shopping, lights and decorations, and joyful carols, Advent is intended to be a season of fasting, much like Lent, and there are a variety of ways that this time of mourning works itself out in the season. Reflection on the violence and evil in the world cause us to cry out to God to make things right—to put death’s dark shadows to flight. Our exile in the present makes us look forward to our future Exodus. And our own sinfulness and need for grace leads us to pray for the Holy Spirit to renew his work in conforming us into the image of Christ.
One catechism describes Advent spirituality beautifully: “When the Church celebrates the liturgy of Advent each year, she makes present this ancient expectancy of the Messiah, for by sharing in the long preparation for the Savior’s first coming, the faithful renew their ardent desire for his second coming. By celebrating the precursor’s birth and martyrdom, the Church unites herself to his desire: ‘He must increase, but I must decrease.’”
Advent and the Christian Life
While Advent is certainly a time of celebration and anticipation of Christ’s birth, it is more than that. It is only in the shadow of Advent that the miracle of Christmas can be fully understood and appreciated; and it is only in the light of Christmas that the Christian life makes any sense. It is between the fulfilled promise of Christ’s first coming and the yet-to-be-fulfilled promise of his second coming that Karl Barth penned these words: “Unfulfilled and fulfilled promise are related to each other, as are dawn and sunrise. Both are promise and in fact the same promise. If anywhere at all, then it is precisely in the light of the coming of Christ that faith has become Advent faith, the expectation of future revelation. But faith knows for whom and for what it is waiting. It is fulfilled faith because it lays hold on the fulfilled promise.” The promise for Israel and the promise for the church is Jesus Christ; he has come, and he will come again. This is the essence of Advent.
Source: http://m.christianity.com/christian-life/christmas/what-is-advent.html