Pagliacci is an Italian opera in a prologue and two acts, with music and libretto by Ruggero Leoncavallo. It is the composer's only opera that is still widely performed. Opera companies have frequently staged Pagliacci with Cavalleria rusticana by Pietro Mascagni, a double bill known colloquially as "Cav and Pag".
The above text from the Wikipedia article "Pagliacci" text is available under CC BY-SA 3.0.