Trick-or-treating is a Halloween custom for children in many countries. Children in costumes travel from house to house asking for treats such as candy (or, in some cultures, money) with the phrase “Trick or treat”. The “trick” is a (usually idle) threat to perform mischief on the homeowners or their property if no treat is given to them. It typically happens during the evening of October 31. Some homeowners signal that they are willing to hand out treats, for example by putting up Halloween decorations outside their door. Others might simply leave treats on their porch.
In North America, trick-or-treating has been a Halloween tradition since the late 1920s. In Britain and Ireland, the tradition of going house-to-house collecting food at Halloween goes back at least as far as the 16th century, as had the tradition of people wearing costumes at Halloween. In 19th 
century Britain and Ireland, there are many accounts of people going house-to-house in costume at Halloween, reciting verses in exchange for food, and sometimes warning of misfortune if they were not welcomed.While going house-to-house in costume has remained popular among Scots and Irish, the custom of saying “trick or treat” has only recently become common. The activity is prevalent in the United States, Canada, the United Kingdom, the Republic of Ireland, Puerto Rico, and northwestern and central Mexico. In the latter, this practice is called calaverita (Spanish for “little skull”), and instead of “trick or treat”, the children ask ¿me da mi calaverita? (“can you give me my little skull?”); where a calaverita is a small skull made of sugar or chocolate.
Since the Middle Ages there had been a tradition of mumming on certain holidays. It involved going door-to-door in costume, performing short plays in exchange for food or drink. The custom of trick-or-treating at Halloween may come from the belief that supernatural beings, or the souls of the dead, roamed the earth at this time and needed to be appeased.
