Quenya is the High Elven Tongue. It was used by those in the Blessed Realm and Númenor, and by those who chose to pass over the sea. It was not only spoken by the Vanyar and Noldor, but also the Valar. In many ways it was seen as an archaic tongue, because it preserved a lot of the features of Primitive Elvish.
The two dialects of Quenya were Vanyarin and Noldorin, but only Noldorin was used in Middle-earth.
Quenya was long estranged from Sindarin, and by the time the language was brought back to Middle-earth, it was already extremely different from the Grey Elven tongue. In the third age, it was usually considered a ceremonial language, rarely used in everyday speech.
It's the most developed of all the languages. In all other words, Quenya is unique in its own way, and in my opinion, wonderful. (obsessed is a word I used quite often :D)