Much has been written about the Gruagachs, and out of a wealth of information from J.F.Campbell and J.G.Campbell, from Alexander Carmichael, Donald Mackenzie and Lewis Spence, three different types of Gruagach seem to emerge.

In the Highlands there is the fairy lady dressed in green with long golden hair, sometimes beautiful and sometimes wan and haggard, who is the guardian of cattle and is a kind of fairy chatelaine to a farm. Mackenzie is inclined to think that she is truly a glaistig and that Gruagach, "the hairy one", is an epithet attached to her. Like the Glaistig she travelled extensively and was connected with water. It was her habit to come dripping into houses and ask to dry herself by the fire.

There were also male gruagachs in the Highlands, some handsome, slender youths wearing green and red, but for the most part naked and shaggy and performing brownie labours about the farm which they patronized. Both kinds had offerings of milk made to them.

In northern Ireland the grogans followed the brownie tradition, but in southern Ireland, the Gruagach was a supernatural wizard, often a giant after the style of the Wizard in night naught nothing. A clear account of all these three gruagachs is given by Lewis Spence in "The Fairy Tradition" (1328; 1290: p.206-207, Motifs: F480, F488.1).