The term "Dark Elf" is variously thought to have arisen as a reference to either their skin tones, their habit in some areas for subterranean dwelling, or as a comment on their ethics and morals.
Drow are not common, but they are found in a variety of areas on the Alusian and Terranovan continents. The Drow of Terranova are somewhat different from their Alusian cousins and an argument could be made for them being a separate sub-race but they do share some common history and culture.
Physically Drow have Elven builds and attributes, but show a somewhat wider range in skin tones, ranging from extremely pale through tanned, and into the darkest ebony.
The history of the Drow people is shrouded in mystery although records have shown the Drow tongue used by many Elven secret societies prior to the War of Tears. Debates continue amongst the Elven people as to the source of this language but it is believed that the creator was a being of great power and the key to that power was hidden within the language. When the War of Tears broke out the Elven nation fragmented and those who continued the search for this knowledge eventually became the Drow as we know them today.