Short answers, pulled from the story.
The elf first appeared as a player character race in the original 1974 edition of Dungeons & Dragons. This race emerged from the creative minds of Gary Gygax and Dave Arneson as a creature designed to be more capable than humans while remaining limited by specific game mechanics.
Elves in Dungeons & Dragons live more than half a millennium and reach physical maturity by the age of 25. They achieve emotional maturity at around 125 years old, which creates a significant psychological distance between elves and shorter-lived human counterparts.
The dark elves led by the matron goddess Lolth broke from the primary elven pantheon during the Crown Wars and were transformed into drow. They were subsequently banished to the Underdark, creating an undying hatred between the surface elves and the drow that persists for thousands of years.
The rockseer elves, also known as deep elves, are the rarest of all elvenkind in Dungeons & Dragons. These elves are far taller than most of their kin and reach almost eight feet in height with silver hair and pale ice-blue eyes.
The half-elf appeared as a player character race in the original Player's Handbook in 1978. In the Forgotten Realms setting, the majority of half-elves come from parings between humans and moon elves.
Wizards of the Coast announced in December 2022 that the word race would no longer be used to refer to a character's biological traits. This change was replaced with the word species and went into effect with the December One D&D playtest release.