What's now an annual holiday full of fun and scare, was once a very important tradition that all originated with an ancient Celtic Festival. People would light bonfires and wear costumes to ward off ghosts. In the beginning of this tradition Halloween was known as All Hallows Eve, which took place on October 31st, the day before All Saints Day. It started with the celts who lived in Ireland, the United Kingdom, and Northern France. Halloween typically marcks the end of summer and the harvest, and the beginning of the dark, cold winter. It was associated with human death. Celts believed that on October 31st the worlds between living and the dead became blurred or merged together, they believed that at the time when the worlds blurred ghosts of the dead returned to earth. Another belief that they had was on Halloween when the ghost or spirits came out they made it easier for the druids, or Celtic Priests to make predictions about the future. What they did to protect themselves from these ghosts wa building bonfires every year on October 31st as sacrifices.
There are a lot of smaller traditions that go along with Halloween, such as soul cakes. What they did with soul cakes was every year the day before All Saints Day, in the catholic religion, they used to hand out these small rounded pastries to the poor and sick. In return for the pastries they were to promise to pray for family of the dead and also their dead family members. Another small tradition, which was a myth was the black cats. What they believed was that when a black cat crossed your path you were now cursed. Over the years the traditions changed and soon they turned into fun and games and a day for people to just each a lot of candy.