Sometimes, "fairy" refers to the diminutive woman with butterfly wings that is well-established in pop culture. However, it is worth mentioning that the term can refer to a wide range of supernatural entities in a wide range of places. There isn't a consensus on what fairies are supposed to be. Popular theories include but are not limited to not quite angels, not quite demons, pre-Christian deities, the spirits of the dead, and the spirits of nature. This makes sense because fairies don't come from a single source but rather from multiple sources.
In Wales, fairies are called the Tylwyth Teg, which means something along the lines of the "Fair Family." Perhaps unsurprisingly, they share a lot of similarities with their cousins throughout the British Isles, with the result that they show up in a lot of similar stories. For example, there are stories of human men getting married to fairy maidens, who were still required to abide by the taboos of their kind. Similarly, there are stories of human women choosing to live in the world of fairies, which meant great wonder at the cost of abandoning their human ties. Other stories range from fairies riding out in great processions to clever parents having to recover human children that have been switched out for changelings.
Of course, there are also more stand-out stories about fairies in Welsh mythology. For proof, look no further than Morgan le Fay, who is something more than human even in her most familiar form as King Arthur's sister. In fact, King Arthur himself is entwined with fairy lore, as shown by the stories of him ruling Avalon as well as riding out on the Wild Hunt.
