The word “Advent” means “coming”. By the 4th Centruy, the first evidence of Advent is written from the Council of Saragossa, Spain in 380 AD
Advent has a double meaning. The first two weeks of Advent the scripute readings look to the 2nd coming of Christ. The last two weeks of Advent have to do with the first coming of Christ in Bethlehem. The early Church Fathers of the Church wrote about a 3rd coming of Christ, that is Christ comes to us each day in scripture, sacraments and in prayer.
Advent is the beginning of the liturgical year and is a time of deeper prayer, fasting and repentance. Advent prepares us for the first coming so that we are spiritually sharp. The challenge is that we need to be always spiritually sharp for today and at the end of time.