Silvan Elves were of Nandorin descent but they were mainly governed by Sindar and Noldorin rulers. Examples of such rulers were Thranduil, king of the Woodland Realm in Northern Mirkwood, Amdír and his son, Amroth, who ruled over Lorien, and Galadriel and Celeborn, who too ruled over Lorien.
The Silvan Elves of Mirkwood, formerly known as Greenwood the Great, were known to be distrustful of dwarves but friendly to Men, with whom they trade. Mirkwood had been called Greenwood the Great until around the year TA 1050 of the Years of the Sun, when the shadow of the Dark Lord Sauron fell upon it, and men began to call it Mirkwood. During his journey to the Lonely Mountain (Erebor), Bilbo Baggins had to rescue the Dwarves of Thorin II Oakenshield's company from these Elves. These Elves were also one of the armies in the Battle of the Five Armies.
Legolas of the Fellowship of the Ring, although he lived among them and presented himself as one of the Silvan folk, was not one of them. As a son of the Elven-king Thranduil, who had originally come from Doriath, Legolas was actually at least half of Sindarin heritage on his father's side (his mother's identity is unknown, though it is likely she was of Silvan background). This was complicated by the fact that a small minority of Sindarin Elves ruled the predominantly Silvan Woodland Realm of Northern Mirkwood, a minority to which Legolas belonged. The Sindarin minority in that realm, who should have been nobler and wiser than the Silvan Elves, could be seen as having "gone native" at the end of the First Age after Morgoth was defeated and all the grand elf kingdoms of Beleriand were destroyed.
In the cartoon version of The Hobbit, they have been depicted as having green skin and brown clothes which were very primitive in comparison to the other elves portrayed in the movie.
The Silvan Elves of Lórien were known as part of the Galadhrim, literally "tree-folk". However, the Galadhrim of Lorien also included a mixture of elves of Nandor, Noldor, and Sindar descent. Galadriel was of Noldor descent, being the daughter of Finarfin, while Celeborn was of Sindarin descent of the Kingdom of Doriath. At the time of the War of the Ring they spoke an accent or dialect of Sindarin which had changed so much that Frodo Baggins, who spoke Sindarin, could not understand them. Additionally, few Elves of Lórien could speak Westron, so that Haldir, one of the few that could, had to accompany them on their way to Caras Galadhon. Haldir has been speculated to be a Silvan Elf, but there is no absolute evidence to confirm this.