Boxing day is celebrated in England, Canada, Australia, Scotland, and South Africa. It is either held on December 26th, or on the first weekday after Christmas, depending on local tradition. Gifts and monetary donations are given to the needy, and government offices and many businesses are closed (but not the malls). Small gifts may be given, particularly to children.
No one really knows where Boxing Day comes from, but here are some theories:
In the grand old days, servants worked through Christmas, but were given the day after Christmas off. Their employers gave them boxes of gifts to reward them for their service.
Also, December 26th is St. Stephen's Day. St. Stephen was charged with giving food to the poor; the tradition of giving to the poor on Boxing Day probably comes from this. It's possible that its name also come from the tradition of churches opening up their poor boxes on this day.