In J.R.R. Tolkien's mythology, the Calaquendi were the "Elves of the Light", Elves who had gone to the Western Land Valinor, and seen the light of the Two Trees before they were poisoned and died. The Elves are subdivided into many groups based on whether or not they followed the call of the Vala Orome who called them to journey from the far east of Middle Earth to Aman, the blessed land. Some chose not to go, while some chose to go but didn't complete the journey, and only the Calaquendi, also known as the High Elves, finished the journey and saw the trees in bloom, shining with a light purer and more beautiful than the later light of the sun and the moon. The opposite term is Moriquendi, Elves of Darkness, which is sometimes used in the pejorative sense. It is not totally clear who the terms could apply to. Elves born after the trees had died perhaps would be technically known as Moriquendi, but were probably not considered as such.
The internal description of who the Calaquendi were being made, I want to point out one of the more interesting ways that they fit into Tolkien's history, and how it might give us some insight into Tolkien criticism. One of the most obvious metaphors that run across Tolkien's writings is the struggle between light, and dark. For some readers, this is interpreted as a simplistic struggle between the good, just, beautiful light against the bad, cruel, ugly darkness; an interpretation that has led some to believe that Tolkien was perhaps racist. Even those who don't believe that Tolkien was trying to intentionally group the world into good and bad may sometimes grow tired of the description of the beautiful, blessed and goodness of those who have seen the light.
So what is interesting in regards to the Calaquendi, those who saw the light of the trees, and who also learned philosophy in the city of the Gods and Angels is that at no point are those "of the light" portrayed as being more wise, moral or compassionate than those of the darkness. The entire Silmarillion is about the devastating war and civil war that one group of elves, the Noldor, who were Calaquendi, fell into. Feanor, the greatest of the Elves, and one who had an intimate relationship with the light of the two trees, also commits fratricide against one of his fellow tribes, and then abandons his brothers, nephews and nieces. His children, also Calaquendi, are portrayed throughout the Silmarillion as cruel, arrogant and perhaps craven. Elwe, another Calaquendi, also lets greed and possessiveness lead him and his people towards a road towards destruction. Of course, some of the Calaquendi, such as Fingolfin and Turgon, are portrayed as moral and courageous, although not without blame. On the other hand, many elves that did not see the light of the trees-- such as Cirdan, Luthien and Beleg -- are portrayed very positively. The full histories and personalities of all characters in the Silmarillion would take a long time to write, but any reader who wishes to can investigate the book and study to see whether the status of Calaquendi had any bearing on a character's behavior. The fact that many times it seems not to is one of the pieces of evidence that Tolkien's myths are not quite as clear cut in good vs. evil as they may seem to be.