As you may recall, After the awakening of the Elves, Oromë was sent to bring them to Valinor. Some of the Elves refused to go, however, and were dubbed the Avari (the Unwilling), and they drifted off to forests and caves. Others started the trip but stayed behind without crossing the Misty Mountains; these basically became the Sindar. The Sindar, by and large, became the Silvan Elves, and they’re part of recorded history, while very little is ever really recorded about the Avari.
At the end of the Third Age, most of the Calaquendi (the Elves who did go to Valinor) depart for the West by ship, with a few stragglers following later. What happened, though, to the Silvan Elves and the Avari? Did they finally opt to go West? Would they have been allowed aboard the ships? Or are they still lurking in shadowy forests to this day?
Side question: When the Calaquendi are killed (in battle, say), their spirits go to the Halls of Mandos in Valinor, to rest, recharge, and get re-bodied. Nearly all of them then stay on in Valinor as opposed to returning to Middle-Earth. What happens to the Sindar or the Avari when they die, though? Do they wake up in Valinor, where they never wished to go?