Trick-or-treating is a popular Halloween tradition where children dress up in costumes and go door-to-door in their neighborhoods. They knock on doors and say "trick or treat," which prompts homeowners to give them candy or other treats. This activity usually takes place on the evening of October 31st and is enjoyed by kids of all ages. The origins of trick-or-treating can be traced back to ancient Celtic festivals, where people would dress in costumes to ward off spirits. Over time, this evolved into the modern practice we see today, where communities come together to celebrate Halloween and share in the fun of costumes and candy.