A good piece from Dr. Witherington.
Incarnation is a big word, and sadly, not a lot of Christians either use it, or know what it means. It does not refer to the same thing as the virginal conception, though the latter is the means by which the incarnation of the Son of God took place. Incarnation refers to the choices and acts of a pre-existent divine being, namely the Son of God, that the Son took in order to become a human being. He took on flesh, and became fully, truly human without ceasing to be fully, truly divine.