What makes a fairy tale?

I was writing a series of fairy tales and was wondering, what exactly makes something a "fairy tale"?

At first I thought it was some sort of supernatural element, but you got Bluebeard which is just a serial killer story. So I thought romance. But then you got Emperors New Clothes. So what is a fairy tale per se?

I'm not really an expert so I may be a bit off but I believe It's mostly just a term for folk tales. On that note there are some books and pages on folk tale patterns but mostly they're tales folk tell each other. Stories parents tell to kids that they learned from their parents, those dirty jokes that have been around forever. Not too many unique features other than being signs of the culture they came from. If it helps some of the most common types of folk stories are either cautionary or trying to teach something. Bleh, never was good at explanations but hopefully this giant wall of text helps you somehow.

Judging by how I see the books organized at the library it seems like fairy tales have supernatural elements to them even if that just includes animals talking. The children's books that are not fairy tales are more realistic.

So if one were to create their own fairy tale, what elements must one have in the story so that the story can call itself a fairy tale?

I'm not sure you technically can buuuut, you can make it feel like an old fairy tale. I'd recommend a very simple writing style without much description or characterization so people wouldn't have trouble memorizing it, use of "sacred numbers" like 3, 7, or 12, and frequent repetition of some key phrase or description. For further reading this very wiki has pages on both fairy tales and fairy tale tropes, and I'd highly recommend reading hero of a thousand faces by Mr. Campbell or at least a summery of it.

They are often metaphors trying to explain things, or morality lessons framed in a magical setting (for example: "It's good to help people" but instead of helping a person, you help a talking animal). The protagonists could very well be nameless and referred to by one of their individual traits (such as 'The Little Match Girl' or 'The Little Mermaid').

They also tend to be short, as they were originally passed down by oral storytelling. Not even modern short-story length. In a standard collection of traditional fairy tales such as Andrew Lang's Fairy Books (which collects them from various countries, not just Germany like Grimm), they would rarely last more than a few pages.

There was an article written a while back that talks about that fairy tale essence and how they're as told via video games, so I'd recommend taking a look at that if you're hungry for a second opinion. Doubly so if you're a fan of Ni No Kuni...which I'd argue anyone should be, but whatever.

Hope it helps you out.

It's the atmosphere of wonder and terror that makes a fairy tale fey, not monsters or magic, which can be represented by ordinary people and mundane objects. A fairy tale draws you into a world of enticing danger and sinister freedom. At least, that's what I feel about fairy tales.

Anyway, I try to inject that essence into my work but it gets lost in all the overzealous world-building I tend to do.