The people of Mexico prepare and celebrate Christmas a little earlier than most of the people in the United States. They have their own traditions. A lot of them like to celebrate 9 nights earlier up until Christmas Eve so they start on December 16 because of the posadas and continue to celebrate every night until December 24.
The posadas are when the neighborhoods gather together and visit a different host house or store each night. The people at the host house give out gifts and food, Normally they give gifts for the kids (such as toys.) The food they give out to the many people includes tamales, empanadas, and bread. The next night, everyone meets at that place then walks together to the next house or store. On the way, they like to sing songs. This most likely the same routine until December 24, which is often the largest gathering.