These notes primarily taken from Baker's Evangelical Dictionary of Biblical Theology:
Apart from Jesus Christ, John the Baptist is probably the most theologically significant figure in the Gospels. He was not a writer or traveler, yet I repeat---apart from Jesus Christ, John the Baptist is probably the most theologically significant figure in the Gospels. As was the case with Jesus, his birth was meticulously recorded (Luke 1:5-25). His entrance into the world was marked by angelic proclamation and divine intervention (Luke 1:57-80). John's birth not only parallels that of Jesus's, but echoes the momentous occasion of the birth of Isaac to Abraham and Sarah (Gen 17:15-22 ; 21:1-7). John is clearly a pivotal figure in the salvation history of God.