The document summarizes the origins and traditions of Halloween. It began as an ancient Celtic festival held on October 31st, which marked the boundary between the living world and the spirit world. When the Romans conquered the Celts in the 1st century AD, their festivals were combined. In the 800s, the Catholic Church established All Saints Day on November 1st and All Souls Day on November 2nd, which eventually merged to become Halloween. Halloween traditions spread from Europe to America and took on new customs like trick-or-treating, pumpkin carving, and costumes. Today it is celebrated in many countries with regional variations but generally involves honoring the dead and spirits.