Dark elf

Dark elves, were elves, known as Ssri-tel-quessir in the elven tongue, and were the ancestors of the drow. The two terms were oftentimes used interchangeably, even by elves (Tel-quessir) themselves.

Dark elves had been high elves

They were not the same as wild elves or their ancestors as the curse of the Descent would have then fallen on the wild elves as it had the Miyeritari.

Dark elves had dark brown skin, as opposed to the ebony skin that drow presently have. They also may have had black hair instead of white and no darkvision. Dark elves were also not tainted with Wendonai's blood.

History
Roughly, twenty-seven millennia before the raising of the Standing Stone, the Fey creator race opened gates to the Feywild in an effort to undermine the ruling dragon empires. Through these portals, the first elves immigrated to Toril. These green and dark elves worship the Faerie gods (not the Seldarine, which were unknown at this time). Although most green elves were content to remain in small scattered tribes, one group known as the Ilythiiri, negotiated a truce with dragonkind and began carving out a small kingdom in the south. The great Ilythiir capital at Atorrnash would remain a shining beacon of elf culture for millennia.

Other dark elven nations would later arise including the realm of Miyeritar, located in what is now the High Moor.

Wendonai was a balor lord who, in -11500 DR was tasked by Lolth to seduce the Sethomiir clan, rulers of the Ilythiiri into her worship and grant them evil magics. He succeeded and was probably the greatest (but by no means the only) influence on the fall of the dark elves.

In -10500 DR, during the Crown Wars, the High Mages of Aryvandaar cast a fell high magic ritual that completely destroyed the dark elven nation of Miyeritar in an event called the Dark Disaster, changing that realm into a large swampy expanse known as the High Moor.

During the Crown Wars, the Ilythiiri made several unsuccessful attempts to conquer Faerûn (although they conquered Southern Faerûn up to Shantel Othreier), and at the time of the Fourth Crown War, they turned to Lloth and the other outcast Seldarine in the Demonweb Pits who gave them powerful magic and fiendish allies as a reward for allegiance. After many malicious acts and abuses of elven magic, Corellon Larethian banished the "Dhaerow" (traitors) whom Lolth used to be responsible for (and most of whom still secretly worshiped her) to the Underdark. It was at this time that all dark elves were physically transformed into drow, their skin becoming much darker.

In 1374 DR, Khelben "Blackstaff" Arunsun brought together many powerful mages in order to restore the denizens of the lost city of Miyeritaar's High Mages and cleanse part of the High Moor. In order to make the magic permanent, he and the Grand Mage Ualair the Silent sacrificed their lives to restore Rhymanthiin, the Hidden City of Hope.

Later, Q'arlynd Melarn managed (through a High Magic spell, with the aid of Eilistraee) to transform those drow that took up Eilistraee's dance back to their ancestral physiology as dark elves and they physically reverted to their brown-skinned dark elf form. Drizzt was not among those "redeemed dark elves," and his skin remained ebony because only followers of Eilistraee were affected by the High Magic spell.