Like the Celts, the Europeans of that time also believed that the spirits of the dead would visit the earth on Halloween. They worried that evil spirits would cause problems or hurt them. So on that night people wore costumes that looked like ghosts or other evil creatures. They thought if they dressed like that, the spirits would think they were also dead and not harm them.
They went dressed up as angels, demons or saints. The soul cakes were sweet, with a cross marked on top and when eaten they represented a soul being freed from purgatory.
Google is celebrating Halloween with a video of Jinx, the lonely ghost, who embarks on a mission to find the perfect costume - and a place to belong.