ChristmasSimply put, Christmas is the celebration of the birth of Jesus Christ. Additional input:
Traditionally, it's supposed to be a celebration of the birth of Jesus Christ. Historically, it's "winter festival". Christmas is just a couple days following the "shortest day" for the northern hemisphere. That means that the north poll of the earth's axis is pointing AWAY from the Sun. As the earth continues it's trip around the Sun, the days start to get longer. According to older European celebrations, when the Sun started back north, there was reason to celebrate and that was the beginning of the Winter Festival. When Constantine united Europe under the "Universal Religion", he incorporated several of the more familiar holidays into the religion he needed to unite Europe. Winter festival is about the rebirth of the land so it was generally felt that Christmas would fit in. While Constantine's efforts to unite Europe eventually failed, his Catholic (universal) religion continues today.
Check out some books by John M. Allegro, as I understand he is a professor at Salford University. He helped decipher the Dead Sea Scrolls. One book of his in particular, called the "Sacred Mushroom and the Cross," explains many links between the old traditions from the Pagan rituals that have been adopted by the Christian faith. It will explain some of the reasons we use Santa, the reindeer, the red and white colors, etc. He also explains how some of the miracles that Jesus performed can be easily explained with everyday occurrences -- all very interesting and rather controversial. I would be happy to divulge more if you have the time and you are interested.