Halloween History
Most people probably know of Halloween as a contraction of the words "All Hallows Evening". This means it is the evening before "All Hallows Day".
All Hallows Day is also known as All Saints Day, and occurs on the 1st November. It was traditionally a Christian feast celebrating all Christian saints, especially those who had been martyred. In the Catholic Church, All Saints Day celebrates those who have gone to heaven, and is followed by All Souls Day, on November 2, for those who have died, but not yet gone to heaven.
Trick-or-treating apparently partly comes from the English medieval practice of "souling", when poor people would go from door to door offering prayers for All Souls Day, in exchange for food. This is referred to by Shakespeare, when he says "like a beggar at Hallowmas."
At the same time of the year, in Celtic history there was autumn festival called Samhain, celebrating the end of summer with a "fire festival" or feast. It was believed that the dead would visit earth at this time, and the bonfires were necessary to scare off evil spirits.
Another recent celebration that has merged with Halloween is Guy Fawkes Day, in the UK, which celebrates the failure of Guy Fawkes to blow up the Houses of Parliament in Westminster on 5 November 1605. Traditionally a bonfire was lit, with a dummy of Guy Fawkes being burnt.
These days, if you know there are children in the area who like to dress up and trick or treat, it has become accepted practice to have lollies available to hand out. And to indicate that you have run out of lollies by taking down your decorations, otherwise you may expect the "trick", as you don't have any "treats".