From LotR: Appendix F
Elves has been used to translate both Quendi, 'the speakers', the High-elven name of all their kind, and Eldar, the name of the Three kindreds that sought of the
Undying Realm and came there at the beginning of Days (save the
Sindar only. This old word was indeed the only one available, and was once fitted to apply to such memories of this people as
men preserved, or to the making of Men's minds not wholly dissimilar. But it has been diminished, ant to many it may now suggest fancies either pretty or silly, as unlike to the Quendi of old as are butterflies to the swift falcon - not that any of the Quendi ever possessed wings of the body, as unnatural to them as to Men. They were a
race high and beautiful, the older
Children of the world, and among them the Eldar were as
kings, who now are gone; the People of the Great Journey, the people of the Stars. they were tall, fair of skin and grey-eyed, though their locks were dark, save in
the golden house of Finarfin; and their voices had more melodies than any mortal voice that now is heard. They were valiant, but the history of those that returned to
Middle-earth in exile was grievous; and though it was in far-off days crossed by the fate of the Fathers, their fate is not that of Men. Their dominion passed long ago, and they dwell now beyond the circles of the world, and do not return.