William Butler Yeats, in Irish Fairy and Folk Tales, divided them into the Trooping Fairies and the Solitary Fairies. 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 contained the aristocracy of the fairy world, including the Irish Daoine Sídhe. They were known as trooping faeries because they traveled in long processions, such as the one from which Tam Lin was rescued. But the trooping fairies also included other fairies of lesser importance; a trooping fairy could be large or small, friendly or sinister.
The Welsh fairies, Tylwyth Teg, and the Irish Sídhe were 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. _Wikipedia