Halloween is a holiday that originated from the ancient Celtic festival of Samhain, where people would light bonfires and wear costumes to ward off ghosts. Now, on October 31st, children dress up in costumes and go trick-or-treating by visiting neighbors' homes asking for treats like candy. Common Halloween symbols include black cats, bats, ghosts and witches. People also carve pumpkins into jack-o'-lanterns to use as decorations or to light with candles.