In Norse Mythology Dark Elves are referred to as Dökkálfar, primarily mentioned in a compilation from 13th century Iceland called the Prose Edda they are depicted as hideous creatures that live beneath the ground and are 'blacker then pitch', the Dark Elves are also described as very annoying and up to no good. There are also mentions of Dark Elves called Mare's that will sit on your chest while you sleep and whisper dark things to you causing terrible nightmares. Similar to many other depictions of Dark Elves the Norse version is very sensitive to light and will turn to stone if hit directly with sun light.
Another potential version of Dark Elves would be the Svartálfar (meaning Black Elves), a dark creature living beneath the ground in a place called Svartálfaheimr that among other things crafted replacement hair for Sif and the unbreakable chain that binds Fenrir. It is unclear however if the Black Elves and Dark Elves are in fact the same type of creature, however there are certain similarities between them. Black Elves are also believed to potentially be another word for Dwarves.
The Dark Elves of the Forgotten Realms setting or Drow as they are more commonly referred to as were once a surface dwelling race that were driven underground after their goddess Lolth (known as Araushnee before her fall) betrayed the rest of the Seldarine (the elven gods) and were cast down into the abyss for her treachery. As Araushnee their goddess were known as the goddess of destiny and artisans but once she became Lolth her domains became more about darkness and spiders and other evil things that would deeply influence Drow society.
Once underground the Drow became the primary inhabitants of a vast network of caves known as the Underdark, an environment that is extremely hostile to outsiders and filled with a huge variety of extremely dangerous creatures including the much feared Illithid's and Beholders, adapting to such a hostile environment would strongly affect the evolution of the Drow making them very resilient and resistant to magic spells, it would also grant them the ability to see extremely well in the dark but at the cost of a sensitivity to direct sun light.
The drow are a matriarchal society meaning that women are typically considered superior to men and very few men can take on leading positions within the society, the biggest exception would be if the male were very proficient in wizardry, although he would still technically be inferior to the lowest rank females he would gain some degree of worth due to his usefulness and rarity. Drow Society is typically runned by houses which are basically big families that frequently compete with each other for strength and status, climbing the ranks within your house often involves murdering your direct superior as an unwritten rule, while murder is still illegal getting away with it is part of the process as it displays your power and treacherous ability which is valued within drow culture.
While the vast majority of drow follow the goddess Lolth and are deeply influenced by her there are certain factions that follow other drow gods, a few popular examples would be gods such as Vhaeraun who is often followed by male drow, or Eilistraee who is revered by by the few good drows that has decided to live at the surface.
Other notable features about Drow society include the revering of spiders in large part due to their goddess Lolth being cursed with the shape of a half woman and half spider, as such any hostile act towards spiders are considered heresy. The Drow are also bi-lingual with one spoken language and one language that consists of hand gestures and facial expressions, most drows are also proficient in undercommon as well as other languages depending on their region. The capital of drow society is Menzoberranzan located in the northern parts of the underdark, Menzoberranzan is also the home of one of the most popular drows known as Drizzt Do'urden.