Quenya is the Tolkien language commonly called the language of the High Elves.
Tolkien developed Quenya as an Elvish language inspired partly by Finnish, Latin, and Greek. In his mythology, it was associated especially with the Eldar and with the Elves who lived in Valinor or descended from them.
Quenya remained an important ceremonial and literary language in Middle-earth, while Sindarin became the more widely spoken Elvish language among many Elves there. Tolkien constructed grammar, vocabulary, sound systems, and historical changes for both languages rather than treating them as collections of invented words.
The term “High Elves” can refer to Elves who made the Great Journey to Aman, so context matters when discussing Quenya. Sindarin is not the same language, even though the two are related within Tolkien’s fictional history.