Over 2,000 years ago, the Celts in Ireland created a festival called Samhain which was a day to celebrate the end of harvest and the beginning of Winter. They believed that during this time, the dead and living merged and for this reason, they would light bonfires and wear costumes (in an attempt to disguise themselves) to ward off any evil spirits.
The Christian Church then adapted Samhain and turned it into a three day festival which started with All Hallows Eve - later known as Halloween, followed by All Saints Day was took place on November 1st and ended with All Souls Day. It was a way to remember and honour the martyrs, Saints and the Dead - both known and unknown.
Then it was slowly introduced to North America where it snowballed into the celebration that we recognise today!
There isn't a complete agreement on who took the idea from who, however the carving of vegetables came from an Irish legend where scary faces were carved into root vegetables like turnips and then were used as lanterns which were then placed by windows and doors to frighten off any evil spirits. Later, when Halloween was taken to America, they substituted the turnips for pumpkins, which is what we use today.
I know what you're thinking... this isn't very magical, where is the witchcraft? Where are the sacrifices and satanic cults? Well, in the early nineteenth century, the poor witches got all wrapped up in Halloween and the occult. People started dressing up as a classic fairy-tale witch, hoping to stay protected from the evil spirits, they would also offer a treat to the evil ones to avoid receiving a trick, this is where our 'trick or treat' came from.
But where there is a belief that the living and dead can coexist for a night, there will be talk of magic and the supernatural. But really...there is nothing in the history of the original Halloween to suggest anything terrifying or wicked. That is something which has slowly evolved over the generations. With the use of Halloween related horror films, ghost stories and talk of the dead blending into our world, imaginations have rolled with it which has resulted in the Halloween that we know.
For me personally, and my inner hidden goth, I love the Halloween that we experience now! I love a horror film and ghost stories, I love how the kids get to enjoy parties together and dressing up, I also love treats! So whatever the reason, it's a nice excuse to be social, have a good time and go knocking for sweet treats! Now I must dash, I have a pumpkin to carve, No turnips here...