The Tylwyth Teg (Welsh: "the Fair Folk") is the common term in Wales for fairies. A synonym, Bendith y Mamau, means "Blessing of the Mothers". Until the early 19th century it was commonly believed that the Tylwyth Teg, described as ethereal, beautiful and fair-haired, dwelt in a number of places in Wales as genii loci similar to Greek nymphs, Norse elves or Irish Aos Sí. Such places included the lake Llyn y Fan Fach. Tylwyth Teg had Fairy paths upon which it was dangerous for a mortal to walk.
They are usually portrayed as benevolent but capable of mischief, neither entirely good nor completely evil, unlike the Scottish division into Seelie and Unseelie. In their benevolent capacity they might, for example, reward with gifts of silver a woman who kept a tidy house. Yet they might also leave a changeling child in place of a human baby. They are said to covet beautiful mortal children. They fear iron, so unbaptized children could supposedly be protected from them by placing a poker over their cradle.
In many accounts, their king is said to be Gwyn ap Nudd. Types include 'Jili Ffrwtan,' 'Coblynau,' and 'Ellyllon' amongst many others.