Originally Posted by
Seleukos_I.
Well not really. As far as I understood it Dark Elves are the one that refused to join the path to Aman and stayed in the East forever.
Those are the Avari, "the Unwilling". The Calaquendi, "Light Elves", are those who saw the light (of the Two Trees). The Moriquendi, "Dark Elves", are those who did not see the light. The Silmarillion specifically notes in the death of Thingol that he, unlike his (Sindarin) subjects, was a Light Elf, someone who saw the Two Trees.
Then befell the first sundering of the Elves. For the kindred of Ingwл, and the most part of the kindreds of Finwe and Elwe, were swayed by the words of their lords, and were willing to depart and follow Orome; and these were known ever after as the Eldar, by the name that Orome gave to the Elves in the beginning, in their own tongue. But many refused the summons, preferring the starlight and the wide spaces of Middle-earth to the rumour of the Trees; and these are the Avari, the Unwilling, and they were sundered in that time from the Eldar, and met never again until many ages were past.
...
These were the three kindreds of the Eldalie, who passing at length into the uttermost West in the days of the Trees are called the Calaquendi, Elves of the Light. But others of the Eldar there were who set out indeed upon the westward march, but became lost upon the long road, or turned aside, or lingered on the shores of Middle-earth; and these were for the most part of the kindred of the Teleri, as is told hereafter. They dwelt by the sea or wandered in the woods and mountains of the world, yet their hearts were turned towards the West. Those Elves the Calaquendi call the Umanyar, since they came never to the land of Aman and the Blessed Realm; but the Umanyar and the Avari alike they call the Moriquendi, Elves of the Darkness, for they never beheld the Light that was before the Sun and Moon.
...
Thus Elwe's folk who sought him found him not, and Olwe took the kingship of the Teleri and departed, as is told hereafter. Elwe Singollo came never again across the sea to Valinor so long as he lived, and Melian returned not thither while their realm together lasted; but of her there came among both Elves and Men a strain of the Ainur who were with Iluvatar before Ea. In after days he became a king renowned, and his people were all the Eldar of Beleriand; the Sindar they were named, the Grey-elves, the Elves of the Twilight and King Greymantle was he, Elu Thingol in the tongue of that land.
So the Elves as a whole are the Eldalie. Those who accepted the summons were called the Eldar, which is Eldalie in another form, but was the name given to them in their own language by Orome. Those who refused the summons were called the Avari. Those who accepted the summons, but fell out along the way, were called the Umanyar. Those who accepted the summons and reached Beleriand, but waited for Thingol rather than cross over to Aman, were the Sindar. But those who reached Valinor at the time of the Two Trees were the Calaquendi, whereas the Moriquendi were all those who did not.