Christmas is a special day set aside by the early church to celebrate the birth of our Lord and Savior Jesus Christ.
There are lots of myths surrounding Christmas, even some that Christians buy into without proper study. Many people whine about X being used in place of the word Christ in Christmas, but the true perversion of the word is actually the second part of the word. Christmas used to be Christ Mass, denoting a church service held to honor the birth of Jesus Christ. over the centuries, we have somewhere lost the second S in Christmass to become the word Christmas. This myth says that the abbreviation X-Mas is an attempt to remove the word Christ from the name of the holiday. This is a fallacy, In the Greek, Christ ( which is the anglo-latin spelling), is actually spelled XRISTOS. "For example, the first two letters of the word Christ (cristoV, or as it would be written in older manuscripts, CRISTOS) are the Greek letters chi (c or C) and rho (r or R). "(from http://www.cresourcei.org/symbols/xmasorigin.html)
This is one of the original spellings of Christ used in the New Testament in its authentic language. It was shortened to X soon after the church began to exapand away from Jerusalem, it was quite dangerous to be a Christian, but the early church would use X in places to denote a church or Christian home. They would also commonly use the word ICTHYS, or the fish symbol, but in places where Greek was spoken prevalently, or the church had been established for a length of time, X was a much safer and discreet abbreviation for CHRIST.
This practice died out over the centuries as Christianity became legal, until the late 19th and early 20th centuries when some Communist countries such as the U.S.S.R. began to outlaw religions, including Christianity. The symbol X and the word X-Mas was used in order that Christians in those countries could continue practicing their faith. it has saved the lives of countless Christians throughout the centuries and continues to help Christians preach the Gospel of Jesus Christ in places where Christianity is illegal, or secret.