Trick-or-treat is perhaps the most important activity for children on Halloween. Children look forward to the time of Halloween each year so they can dress up in costumes and go from house to house to ask for treats such as candy or other treats. The children will post the question "trick or treat?" when the host of a house opens the door. The phrase implies (figuratively) that if no treat is given, the children may cause mischief to the homeowners or their property.