Myths tries to explain the origin of the world and its nature.
Fables contain animals who talks and act as humans.
A fairy tale starts in an indefinite place and point in history.
The number 3 and 7 can appear, like three wise men. In the book of Revelation there are seven churches, seven angels to the seven churches, seven seals, seven trumpet plagues, seven thunders and the seven last plagues. Mythological creatures like a unicorn or a dragon can appear in fairy tales.
The main character is good and brave and often comes from poor circumstances. He often leaves his home to go out and save the world. When he does he meet people who want to help him, but also evil trying to stop him. It is common with miracles and magic, both small like making wine of water or big like creating a world from nothing or making a dead man live again.
Evil loses and good prevails in the end.

Someone should write a story like that.

Only children believes in fairy tales. If a grown up would insist that it is real we would call this person delusional, except if the story is the bible, then we would call him or her religious.