The first of the Children of Iluvatar to awaken, the elves are the oldest race in Middle Earth, but their time has passed. Elves had their golden age in the ages before the creation of the Sun and Moon, when there was nothing in the sky but stars. Their word for their own kind is Quendi, which means the Speakers, for when they awoke they were the only creatures who spoke language. They are not subject to diseases and do not age, living as long as the world lasts, or until they are slain by violence. Even then, it is said their spirits remain with the world, and they may acquire new bodies. Early in their history, the elves were split into two groups, the Eldar and the Avari. The Eldar went west on the Great Journey to live near the Valar. Those who finished the journey, and saw the light of the Two Trees in Valinor, are called the Calaquendi, or elves of light. They gained much power and wisdom from living in Valinor. Some of the Eldar, and all of the Avari remained and never saw the Two Trees. So, they are called the Moriquendi, or elves of darkness.
Kindreds of the Eldar
There were three distinct kindreds of the Eldar: The Vanyar were all very fair (Vanyar means "the fair" ) and were very fond of song and poetry, even more so than other elves. They are unknown to Middle Earth in these latter ages. The Noldor were very devoted to craft and knowledge for its own sake (Noldor means "knowers"). The last kindred were the Teleri, or Lindir, as they named themselves (Teleri means "late-comers" or "followers" and was given them by the other kindreds because they were very slow to come to Valinor. In fact, many of them never did reach Valinor and they form the majority of elves still in Middle Earth. Lindir means "singers"). The Teleri who came to the shores of the sea and stayed there are referred to as the Sindar, or grey-elves. They were the subjects of King Thingol and his wife, Melian the Maia. Because of their association with Thingol, who had been to Valinor, and Melian, who was one of the Maiar of Valinor, the Sindar became greater and wiser than the Silvans, but they could not equal the true Calaquendi. This is why they are referred to as grey elves. They are between the elves of darkness and light. Some of the Teleri never even crossed the Misty Mountains; these became the Silvan elves of Lorien and Mirkwood (though the Silvan elves may have Avari blood as well. True Avar elves remained in the East of Middle earth, and little is known of their fate.
Elves today
Eventually, the Noldor returned to Middle Earth under very dark circumstances, and fought a long war against the rebel Vala Melkor, whom they have referred to ever since as Morgoth. Finally, the other Valar came to their aid and captured Morgoth, but the war was so violent that the former lands of the Noldor in Middle Earth were destroyed. Most of the Noldor then returned to Valinor. Only a very few remain in Middle Earth.
Elves still in Middle Earth in the Third Age live in four major communities: Mithlond, or the Grey Havens, founded by Cirdan at the close of the First Age, which is made up of a mix of the three kindreds; Imladris, or Rivendell, founded by Elrond Half-Elven, which is also a mix of all three kindreds; Lothlorien, founded by Silvan elves but now ruled by Galadriel and Celeborn, which is made up of primarily Silvans and Sindar with only a few Noldor; and Amon Thranduil, which was founded by Thranduil and is made up primarily of Silvan elves and a few Sindar. Of the characters met in the books, Gildor Inglorion, Glorfindel, probably Erestor, and Galadriel are Noldor (though Galadriel is part Vanyar). Celeborn, Legolas, and Thranduil are Sindar. Elrond is descended from all three of the Kindreds of the Eldar in some measure, and he is part human as well.
The Peoples of Middle Earth