Boxing Day is a holiday celebrated in Britain, Australia, New Zealand, and Canada. It falls on December 26th, which is also St. Stephen's Day.
St. Stephen was a little known saint who achieved eternal fame by being the first Christian to be martyred for his faith, and he met his death by stoning.
Boxing Day is so called because on this day it was the customary for tradesmen to collect their Christmas boxes or gifts in return for good service throughout the year. Also, it included giving money and other gifts to charitable institutions, and the needy.
The holiday may date from as early as the Middle Ages, but the exact origin is not known. It may have begun with the Lords and Ladies of England, who gave Christmas boxes/gifts to their servants on December 26, or maybe by priests, who opened the church's alms (charity boxes), and distributed the contents to the poor and needy.
In England, this day has become part of the celebrations, of being with family.
A day to visit other relations and to have a rest from the day before, to play fun games.
For some it is good to have the 2 days, as on one of the days you can visit with your parents, and the other day your inlaws.
St Stephen is the patron saint of horses, so Boxing Day became associated with horse-racing and hunting. Other sports are also held on this day like football and rugby.