Advent: a coming into view of something that has been anticipated. We are entering the season of Advent on the Church calendar, a time of celebrating the anticipation of Christmas, the birth of Jesus Christ on Earth. John 1. When Jesus came to Earth, born as a baby, he was not coming into existence. He was coming into view in a new way, revealing to us the face of God. Christ has been alive and active since before the creation of the world. Ephesians, Philippians, Hebrews, 1 Peter, and Revelation all speak of Christ, God's chosen plan for redemption from before the creation of the world.
Adventure comes from the future participle of Advent- what has to happen, the definite future events that are on the horizon. When Christ came as a baby, the cross was in view. He came so that God and man could be reconciled. And as Isaiah foretold, and the New testament writers confirm, Christ's mission on Earth was to bear the sins of the world. All the sins of every person who ever lived from Adam to the last person who will ever live were placed on Christ. He is the atoning sacrifice. And this was not a last minute solution, Revelation 13:8 says he was slain from the creation of the world.
God had a plan, Christ had a plan, to deal with man's sin before it ever took place. His earthly advent was made so that he could have a personal advent in each of our lives. That personal advent begins the adventure of a lifetime. His coming so changes our lives that nothing will ever be the same.