The Christmas story really starts with a tree – not a Christmas tree, but a family tree. It is interesting to note that both Matthew and Luke start their gospels with a genealogy. One is the genealogy of Mary, and the other is the genealogy of Joseph. Both were descendants of King David.
The fact that the Christmas story starts with a genealogy shows us that it's a real story that happened in a real place at a real time.
Gabriel had already informed Zechariah and Elizabeth they would have the forerunner of the Lord as their son. Then Gabriel showed up in Nazareth, one of those cities that was on the way to another city. Nazareth also was a place known for its wickedness. Yet living in this godless place was a godly girl named Mary, a direct descendant of King David.
The angel Gabriel made this announcement to Mary: "Do not be afraid, Mary, for you have found favor with God. And behold, you will conceive in your womb and bring forth a Son, and shall call His name Jesus. He will be great, and will be called the Son of the Highest; and the Lord God will give Him the throne of His father David. And He will reign over the house of Jacob forever, and of His kingdom there will be no end" (Luke 1:30-33 NKJV).
The angel was telling Mary, in effect, "You are a fulfillment of Bible prophecy." Imagine being told that you would be the one to fulfill the words of Isaiah 7:14: "Behold, the virgin shall conceive and bear a Son, and shall call His name Immanuel" (NKJV).