Christmas is a religious holiday commemorating the birth of Jesus Christ, who Christians believe is the Son of God. 

Christmas is derived from the Mass of Christ, a service where Christians remember Jesus' death and resurrection. 

The 'Christ-Mass' service, which took place after sunset and before sunrise the next day, was celebrated at midnight, hence its name, which is shortened to Christmas. 

Christmas is celebrated globally, involving family, friends, and children, as it's a time to remember good things and exchange presents. 

The true birthday of Jesus is unknown, and the celebration on 25th December is based on early Christian arguments. It is likely that Jesus' birth occurred between 2 BCE/BC and 7 BCE/BC.

Christmas, officially celebrated on December 25th in 336, was not an official Roman state festival during the reign of Roman Emperor Constantine. 

Christmas is celebrated on December 25th, according to early Christian tradition, which suggests the day Mary was told of Jesus' birth was March 25th, which is still celebrated nine months later.