J.R.R. Tolkien called the Elves the Eldar in the history of Middle-earth.
In Tolkien’s mythology, Eldar is a name for the Elves who accepted the summons of the Valar and began the great journey west from Cuiviénen toward Aman. The term is especially associated with the Elves of the Great Journey, although their histories divided them into different groups and peoples. The journey is a major foundation of the First Age stories.
The Eldar included groups such as the Vanyar, Noldor, and Teleri, though the Teleri’s long journey produced further divisions. Some Elves reached Aman and saw the light of the Two Trees, while others remained in Middle-earth or stopped along the route. These choices help explain the political and cultural differences among Tolkien’s Elves.
Eldar is not simply another word for every individual Elf in every context. Tolkien also used the term Avari for Elves who refused the summons. The distinction is therefore historical and cultural, not a reference to a separate species alongside Elves.