Christmas is the only holiday observed in America that is both a legal and a religious holiday. Even though it is a Christian holiday, Christmas is celebrated by almost everybody in the world regardless of religious affiliation.
The Christmas story is told in the Bible in both the book of Luke and the book of Mathew. Each book gives a different account of the birth of a child in a stable. That child was Jesus, the Son of God.
Luke tells of shepherds who were watching their sheep when an angel appeared to them. The angel told the shepherds that a Savior had been born in Bethlehem. The shepherds then left their flocks and went to see the Christ child.
Mathew tells of the three Wise men who saw a brilliant star in the sky. The Wise men followed the star, which lead them to the manger where Christ was born. Upon seeing the child they gave Him gifts of gold, frankincense, and myrrh. It is because of this event that we celebrate Christmas.