In J. R. R. Tolkien's legendarium, an Elf is an individual member of one of the races that inhabit the lands of Arda. They appear in The Hobbit and in The Lord of the Rings, but their complex history is described in full only in The Silmarillion, edited and published after Tolkien's death. More details about them are given in the author's other writings edited and published since then, such as Unfinished Tales and The History of Middle-earth. The History of Middle-earth also reveals their textual and conceptual history, as Tolkien had been writing about Elves long before The Hobbit was published.
Elves were sometimes called the Firstborn (Q. Minnónar) or the Elder Kindred (as opposed to Men, the Secondborn) as they were "awakened" before Men by the creator of the universe, Eru Ilúvatar (God). The Elves named themselves Quendi ("the Speakers"), in honour of the fact that, when they were created, they were the only living beings able to speak. The Dúnedain called them Nimîr (the Beautiful), while their usual name in Sindarin was Eledhrim.