It gets its name from the Christian festival that follows it the next day, All Saints` Day, which was originally known as All Hallows Day. This is rather interesting because the roots of Halloween could hardly be less Christian.

The Celtic people of Europe celebrated the autumn harvest, known as the Festival of Samhain. October 31st was also the last day of the year for pagans and therefore signaled the coming of winter, a season that was symbolic with death and evil spirits. The Celts tried to scare away evil spirits, so they carved out a scary face on turnip and placed it in front of their house. This modified turnip is known as jack-o-lantern and comes from legend of “Jack of the Lantern”, an unfortunate man who was cursed to wander around the countryside for all of eternity. When this tradition came to the USA, turnips were replaced with pumpkins.
The colors of Halloween are orange, symbolic of the harvest and autumn leaves and black represents death, night, witches, etc.

Halloween traditions are trick-or-treating(visiting neighbors and collecting sweets) and trying to fill up the sack with sweets, annual office party, where are adults dressed up in wild and spooky outfits or setting up of a haunted house.