Every work of Mozart's is assigned a Kochel catalogue number, referring to the chronological catalogue of his works compiled by Luwdig von Kochel in 1862.  A "K" or "KV" number next to a composition's name indicates this.

His operas are the fullest expression of his ability.  1768's "Bastian und Bastienne," composed when he was only 12, is his earliest strong work, but his masterpieces are 1786's "Marriage of Figaro," 1787's "Don Giovanni," 1789's "Cosi fan tutte," and 1791's "The Magic Flute."

Additionally, he wrote a number of concertos, symphonies, string quartets, and string quintets, as well as chamber music, dances, and masses.