The Sidhe (aka Arch Fey) rule over the fey in Alfheim (the equivalent of The Feywild) and can be divided roughly into two courts, the Seelie and Unseelie courts.  While Seelie and Unseelie are both used to describe the reigning kingdoms, the words are also often used to describe faeries themselves based on their disposition — Seelie faeries known to be “happy, blessed, lucky, fortunate, and good natured, as well as having connotations of bringing good luck,” while Unseelie faeries are more, “dangerous, unlucky, unfavorable, unhappy, unholy, and ungodly.” As such, their kingdoms fall under the same ideals, the Seelie Court being the court of light, and the Unseelie court being that of darkness.

The two courts can be further divided into Spring and Summer for the Seelie, Autumn and Winter for the Unseelie.

Seelie Court

Known particularly for their acts of selfless kindness and generosity, it’s no wonder this court is known as the “Court of Inner-Light,” “The Summer Court,” “The Shining Throne,” or “The Golden Ones.”

Just because they come from the Seelie court, though, not all of these faeries are “good” or “pure” as we humans might expect them to be. While more gracious than their Unseelie cousins, many Seelie faeries are prone to playing pranks on humans and other creatures without concern about the aftereffects. They’re also known to eagerly seek revenge on anyone who wrongs them, though for the most part they’ll at least give you some forewarning of the impending attack.

The Spring Court is seen as the much "calmer" ones to the benevolence of the Fae compared to Summer. The fae of this court are generally polite and bright-eyed and bushy-tailed. These fae are more apt to lure humans in with sweet dew. They also have blossoming curiosity. The Spring Court is strongest during the ends of winter and throughout the spring season, despite the Summer Court having reigned. These fae are peppy, quiet, seductive, emotional, and vernal obviously. The epitome of spring.

The Summer Court represents what people see as the benevolent side of the Fae. The fae of this court are generally considered more polite or mannered, albeit they are still very capable of cruelty (but will be more hush-hush, or subtle about it). The Summer Court has free reign over summer solstice and spring equinox months, and are strongest during that time. Needless to say, the fae of this court are frivolous, venereal, hot-headed and what have you. They are the epitome of summer.

Notable members of the Seelie court

Titania, the Summer Queen: The ruler of the Seelie fey of the Summer Court, Titania is a being of magnificent light and woven enchantments

Oberon, the Green Lord: The living soul of the wilderness and the greatest hunter of all time, Oberon is a being of burning passion.

Poludnica: Known as Lady Midday, this favored child of Titania's court loves to torment mortals with sweltering heat before killing them.

Verenestra: The daugher of Titania and Oberon and the fairest nymph of all, Verenestra is a being of beauty and infatuation.
 

Unseelie Court

The Unseelie, the "Unholy" or "Unblessed" Court consists of the malicious and more evilly-inclined fairies. Unlike the Seelie Court, offense is not necessary to bring down their foes or anyone they choose to bother for that matter. As a group, or the 'host' as we Fae call it, they appear at night and assault travelers either 'physically', emotionally, and/or mentally– especially spiritually ignorant folk. Like the faeries of the Seelie Court, neither are the faeries of the Unseelie court always evil. However, when one of them is forced to choose, they will naturally prefer to harm than help.

The Autumn Court is seen as the equally malevolent side of Fae in comparison to Winter, but much more middling. The fae of this court are generally the ones doing the "dirty work" and "trooping". However, these fae can have much nicer sides than any of the Fae and return great favors. The Autumn Court is strongest during the ends of summer and throughout the autumn season. These fae are strong, mystique, eerie, ravishing all the same, and devious. The epitome of autumn. 

The Winter Court represents what people see as the malevolent side of the Fae. The fae of this court frown upon humans. They're more inclined to talk about their ope cruelty. This makes them look none other than evil, however one chooses to define evil. The Winter Court has free reign over winter solstice and autumn equinox months, and are strongest during that time. By and by, the fae of this court are sensible, chilled, dark, baleful, and what have you. They are the epitome of winter.

Notable members of the Unseelie court

The Queen of Air and Darkness: The ruler of the Unseelie fey of the Gloaming Court, the Queen of Air and Darkness is a being of shadow and intrigue

The Maiden of the Moon: The peerless huntress of the full moon, the Maiden of the Moon is free from all restraints.

The Prince of Frost: Once known as the Sun Prince, the Prince of Frost has become immersed in bitterness, becoming a lord of winter and sorrow

The Sisters of Lament: Once the sisters of the Sun Prince's bride to be, their despair and sorrow has corrupted them into shrieking phantoms on the wind.