You would have to be living under a rock to have not heard of Christmas. It is celebrated across the globe by Christians and non-Christians alike.
Traditions and celebrations vary and are influenced greatly by a person's nationality, culture
and religious background.
However, a few things I've noticed are fairly common during this winter festival:
Celebrating the Birth of Jesus
Putting up and decorating a Christmas Tree
Decorating Homes, Churches, Schools, Workplaces, etc..
Exchanging gifts, going to parties, spending money,
etc..