In all stories (Bible, movie, and carol), Jesus is described as the son of God and/or a human form of God. He is also described as the Messiah, because he was the people's savior, sent by God. The day on which Jesus entered this human world is the day which we celebrate on Christmas.
In the verse:
"This, this is Christ the King,
Whom shepherds guard and Angels sing;
Haste, haste, to bring Him laud,
The Babe, the Son of Mary."
Haste, haste, to bring Him laud,
The Babe, the Son of Mary."
The part of Jesus' birth which is most emphasized is its impact upon others; the way the shepherds guard him and angles sing to him. It expresses his importance to ordinary people (like shepherds) who saw him as their king, due to their belief. Even more than for the shepherds, however, was it important for Mary and Joseph to believe God, as he sent Gabriel to tell them they would be expecting His son. After all, it mustn't be easy to be told that as a virgin one will be to carry a child, and at once the one of God. The Persian Astrologers too showed immense belief and trust in God, as they walked the long way, in oder to follow the king-promissing star.
Jesus' rather unspectacular entrance to our world leaves many questions. Why would he chose such a way to join his people. Well, considering that one of Jesus' major achievements was to show to human kind that He is greater than death. And that so are we, when we believe. He demonstrated this by arising from the dead. To show us that we too can do this, it was important for Jesus to be human and to have lived a human life, just like we all do.