There's plenty of theories, so we've broken them down.
The earliest mention was in the 1830s where a ‘Christmas Box’ was the name for a Christmas present.
It also relates to giving to the poor. Traditionally, there was a box to collect money for the poor placed in churches on Christmas Day and opened the next day - Boxing Day, aka St Stephen's Day.
The Victorians were the ones who made Boxing Day a Bank Holiday in 1871. Around the same time the tradition of giving servants time off to visit the family was growing. Boxing Day was traditionally a day off for servants. Their master would give them a box to take with them. It used to hold gifts, a bonus and sometimes leftovers.
Sailing ships when setting sail would have a sealed box containing money on board for good luck. If the voyage was a success, the box was given to a priest, opened at Christmas and the contents then given to the poor.
Well we do not do much on Boxing Day other than hit the stores for all the sales. Some families have open houses or other gatherings. Its an extra holiday for those who dont get the whole week off.
In Alberta Boxing Day sales are popular, but Ive read that in the Eastern provinces sales are not allowed until the 27th.
There is no one explaination for where Boxing Day originated. The term was first used in Britain and then came across to Canada and some of the other countries when people immigrated.
Some say the tradition came from those Boxing up items to give to the poor on the day after Christmas. Others say it was a tradition for employees to bring a box to work on the 26th in which their employers would put money. Others say that the Church would open its tithe Boxes on Christmas Day and distribute the money to the poor on the 26th. And another version is that it is a day people boxed up their leftovers, etc., to give to the poor.