October 31 has been a holiday for almost 2,500 years. It was not always called Halloween, but ghosts, masks, and costumes have been part of most of the celebrations
Long ago, people called Celts lived in Europe. October 31 was the last day of their year. They believed Samhain, the god of the dead, came in the winter. The Celts lit a fire and wore masks or costumes to scare off ghosts and evil spirits
Christians tried to change Celtic beliefs. Christians called November 1 "All Hallows' Day." This was a day to honor saints. November 2, All Souls' Day, was a day to pray for the souls of the dead. Soon the night before All Hallows' Day was called "All Hallows' Eve" or "All Hallows' E'en" (short for evening).
In England on All Souls' Day, poor people used to beg for coins or cakes. They were given "soul cakes." These were small breads with raisins. Soon, children went door–to–door to ask for these cakes, too.
This may be how trick–or–treating started. Now many children dress up in costumes. They knock on doors and get candy or other treats.
Some towns hold parades and give prizes for the best costumes. Schools often hold parties and let students dress up. Many people decorate their houses with ghosts, skeletons, or witches. Orange and black are Halloween colors.
Most people carve jack–o'–lanterns. In Ireland long ago, people carved turnips and put candles inside. When they came to America, they used pumpkins instead.