Diffrence in folktale genres (legends, myths, sagas and fairy tales)

From the perspective of ethnology, legends, myths, sagas and fairy tales are seen as different folktale genres.

Myths are about gods, demigods, mythical creatures or heroes. And they can be part of religion and rituals. They can also 'explain' and justify existing phenomena in the world.
The word comes from Greek: mythos (oral), logos (word, written record)

Sagas also often explain a geographical peculiarity or a supernatural phenomenon, but sagas are more strongly bound to place and time than myths. They contain many frightening, supernatural elements and tell, for example, about witches, sorcery, ghosts, werewolf,  giants, gnomes, nightmares (the creature, not the dream). Sagas can also tell of brave and strong local heroes, of fearsome robbers, subterranean passages, hidden treasures, bottomless pits and haunted castles.
The word comes from German: sagen (to tell)

Legends have many similarities with the sagas, of which it is in fact the Christian counterpart. Legends describe saints and the miracles they perform, as well as stories about Jesus Christ, Mary, and sacred objects. The story is usually based on true facts and people, Sometimes we know for sure that the person existed, in other cases we don't. In many cases, the stories that are linked to the person have only arisen after their life. It is not always possible to find out whether the events attributed to the person actually took place.
The word comes from Latin: legend (what must be read)

In the vernacular, the terms myth, saga and legend are regularly used differently than as described above, but those are in fact incorrect. For instance, the word “urban legend” should actually be ‘’Urban sage’’ but it doesn’t really have that ring to it.

What differentiate all of the above from fairy tales is that myths, sagas and legends are told as truth. For narrators and audiences, they were/are experienced as non-fiction. The fairy tale is usually told as fiction, and stories in that genre express certain wishful dreams.

Fairy tales are traditional folktales that take place at an undetermined place at an undetermined time and therefore often opens with the words "Once upon a time...".
It is essentially an engaged genre that originally contained the necessary satire and sociocultural rebelliousness. They very often have a happy ending “… and they lived happily ever after”

Schwankmärchen are a form of fairy tale where the goal is not to scare or teach a moral, but just to be funny. It’s a long joke or a story with multiple funny things happening, or simply a pun.
The word comes from German, where it means “Merry tale’’

Fables are closely related to fairy tales, but feature almost only animalistic characters. The animal is then based on the character traits. For instance, a fox is cunning, and an owl is wise. These characters can be fully animals or humanoid animals who wear clothes. Fables are actually more political, they are used to criticize societal structures and are more about morals than fairy tales.
The word comes from Latin: Fabula (story)

All of these stories are very old and been told through different time periods, regions and languages. Therefor, there is never a one true way the story is supposed to go, but multiple different versions.