Quenya is the Elvish language Tolkien created as the high or classical language of the Elves.
Tolkien developed Quenya from an early form called Qenya and modeled aspects of its sound and structure on languages including Finnish. In his fictional history, Quenya was associated especially with the Ñoldor and other Elves of Valinor. It functioned as a prestigious literary and ceremonial language in later Middle-earth.
Sindarin is the other major Elvish language encountered in The Lord of the Rings. Tolkien based much of Sindarin’s development on Welsh, and it became the commonly spoken Elvish language among many Elves in Middle-earth. These two languages are therefore easy to mix up.
Tolkien treated his invented languages as evolving historical systems rather than simple word lists. Their vocabulary, grammar, scripts, and relationships changed as he revised the mythology. Quenya appears in names, poems, greetings, and ceremonial phrases throughout his legendarium.