Elf

Elf (Sindar): The Sindar (meaning Grey People, singular Sinda, although the latter term was not generally used) were Elves of Telerin descent. They are also known as the Grey Elves. They are a sub-group of the Eldar and a further sub-group of the Teleri. They are the Elves that chose to remain in Beleriand.
The Sindar are “grey” perhaps because they were not Elves of the Light, never having actually set foot in Valinor, but neither were they Avari, since they did accept the invitation and set out on the journey (and therefore were technically counted among the Eldar). They are sometimes referred to as Elves of the Twilight. The term grey may also refer to Elu Thingol’s grey cloak. It may also be related to Lindar, the Telerin name for themselves. The name that the Sindar used for themselves was simply Edhil (“Elves”, singular Edhel).

Eladrin (Noldor): The Ñoldor; meaning those with knowledge; adjectival Ñoldorin; were the second clan of the elves. According to legend, the clan was originally called the Tatyar; meaning second ones; adjectival Tatyarin; and founded by Tata, the second elf to awake at Cuiviénen, his spouse Tatië and their 54 companions, but it was Finwë, the first Ñoldo to come to Valinor with Oromë, who became their king, and led most of them to Valinor. The Ñoldor who went to Aman speak Quenya, or more specifically the widely-known Ñoldorin dialect of it. However, fully half the Tatyar refused the call of the Valar, and became counted among the Avari.
The Ñoldor are accounted the greatest of the Elves in lore and smithcraft. Fëanor (son of Finwë by Míriel) was the greatest of their craftsmen, and their second and briefest-reigning High King. When Melkor killed Finwë and stole the Silmarils, Fëanor renamed Melkor: Morgoth (“Black Enemy”), and persuaded the Ñoldor to pursue him to Arda and wage war against him.

Elf

Beleriand: The War of Wrath MarkMeredith