Christmas is not one day. It is really three different days rolled into one. Because of this Christmas is can almost be anything of anyone.
The first aspect of Christmas is the pagan holiday of Yule. Yule for these ancient practitioners was a both a dark day for the death of the sun and also a day when the sun was reborn. It was a festival to honor the coming of the New Year. It should be no surprise that Yule was celebrated on Dec 25th.
Many of the “current” traditions of Christmas come out of this tradition. For Yule pagans would decorate their houses with lights. There was, of course, the Yule log. The hanging of wreaths and mistletoe were a protection from spirits. Presents under trees represented good wishes for the coming year. Even a star on top of the tree was part of the ancient pagan tradition.
Most people equate Christmas with the birth of Christ. For some odd reason many of the pictures of the manger even have snowy scenes, though I doubt it snows much in Bethlehem. The exact date of the birth of Jesus is unknown. Some religious scholars even dispute the year by as much as 4 years. Regardless it does not need to be the exact date to be the date the birth of Jesus is celebrated.
December 25th was likely chosen because of some of the similarities to one of the pagan Yuletide myths (it was also the date on of the pagan gods bore a son). Despite the reasons this date was chosen it has a very important religious connotations for practicing Christians, only Easter being conceivably more important.
Santa would be the modern connotation. Let’s face it, despite the people who want to replace, “Merry Christmas” with “Happy Holidays” Christmas has also become a very secular holiday. Santa Claus is based on an old Dutch Legend of Sinterklaas. The original Santa Claus legends had a little bit religion imbued within them since the legend was tied to St. Nickolas. The VERY old pictures of Santa Claus had him in a Bishops robes.
Most modern interpretations of Santa Claus come from two places. The first is the poem, “Twas the Night before Christmas,” written in 1823, by Clement Clarke Moore. The second place was a few pictures of Santa Claus by famed cartoonist Thomas Nast published in 1863.
Of course since then there have been a lot of creative legends and commercialism poured on top of that. Most aimed at making it a day for children; Frosty the snowman and Rudolph the red nosed reindeer just a couple of these.
Regardless of what version of Christmas people believe in, this day has become more than the sum of its parts. It is a day for tradition and family. It is a day for a religious expression for some people. Of course it is also a day for gifts and a celebration of modern commercialism; both good and bad.