What is Advent?

We observe Advent as part of our tradition & liturgical calendar each year. It is the four weeks preceding up Christmas and the birth of Christ.   
It is a time of anticipation and patience. It is a time of rich images and traditions, both with our families and church.

But where did Advent come from and why?

Here is a short synopsis from Christianity.com

The History of Advent

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.

Advent Today

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