In mythology and folklore, fairies are classified in a variety of ways.
Two of the most prominent categories, derived from Scottish folklore, are the division into the Seelie Court and the Unseelie Court. William Butler Yeats, in Irish Fairy and Folk Tales, further divided them into the Trooping Fairies and the Solitary Fairies.
These categories are generally applied to any fairy-type creature, from elves, pixies and brownies to ogres and giants.
Seelie and Unseelie courts
The Seelie Court is seen as more beneficent toward humans. Seelie means "Blessed" or "Holy" and is akin to German selig and Old English "sælig" - the predecessor of the modern word, "silly" (happy, harmless, beneficial). It is also spelled seleighe - the Irish spelling. They are known to seek help from humans, to warn those who had accidentally offended them, and to return human kindness with favors of their own. Still, a fairy belonging to this court will avenge insults and could be prone to mischief. The most common time of day to see them is twilight. One of the most common type of Seelie Faries are Hobgoblins. Shakespeare's character Puck in A Midsummer Night's Dream is one of the most famous Hobgoblins. While, as part of the Seelie Court, they are most well known by their love of pranks and practical jokes played upon humans. However, they never take the joke too far and can be very kind and generous. Some of the other most common faries of the Seelie Court are the Hobgoblin's Cousin, the Brownie, Ferrishyn, Selkies, and Leprechauns.
The Unseelie (Unholy or Unblessed) Court consists of the malicious and evilly-inclined fairies. Unlike the Seelie Court, no offense is necessary to bring down their assaults. As a group (or "host"), they appear at night and assault travelers, often carrying them through the air, beating them, and forcing them to commit such acts as shooting elfshot at cattle. Like the fairies of the Seelie Court, neither are the faries of the Unseelie court always evil. However, when forced to choose, they will always prefer to harm—rather than help—humans. Some of the most common characters in the Unseelie Court are Bogies, Bogles, Boggars, Abbylubbers and Buttery spirits.
In the French fairy tales of précieuses, fairies are likewise divided into good and evil, but the effect is clearly literary. Many of these literary fairies seem preoccupied with the character of the humans they encounter.
Trooping and Solitary Fairies
Yeats divided fairies into the solitary and trooping fairies, as did James Macdougall in Folk Tales and Fairy Lore. Katharine Mary Briggs noted that a third distinction might be needed for "domesticated fairies" who live in human household, but such fairies might join with other fairies for merry-making and fairs.
The trooping fairies contain the aristocracy of the fairy world, including the Irish Daoine Sídhe. They are known as trooping faeries because they travel in long processions, such as the one from which Tam Lin was rescued. But the trooping fairies also include other fairies of lesser importance; a trooping fairy can be large or small, friendly or sinister.
The Welsh fairies, Tylwyth Teg, and the Irish Sídhe are usually not classified as wholly good or wholly evil.
Unlike the trooping fairies, solitary fairies live alone and are inclined to be wicked and malicious creatures, except for the brownie who is said to help with household chores.
Changelings
A Changeling is said to be a fairy that is exchanged for a human child, usually (though not always) as a prank or an act of vengeance. Fairies are said to make this exchange if the human child's parents have caused the faerie world a serious offence, or if the fae have been attacked in some way. Most modern stories indicate that the exchange is performed as a means of vengeance, and it is almost never depicted as a generous act.
