In Leoncavallo's opera "Pagliacci", Canio is the tragic clown who is deceived and eventually becomes the murderous husband of his wife Nedda (Colombina in 'Commedia dell'arte'). He is the head of a group of travelling players in 'Commedia dell'arte'. Canio and his wife Nedda are the leading roles in the public play that they perform.

In the play, Canio plays the clown Pagliaccio, husband of Colombina. The plot line of the play requires Pagliaccio to find out that Colombina is cheating on him with another man Harlequin. This is supposed to be played for laughs. Just before the play is due to begin, Canio discovers that Nedda really is cheating on him. This tragically affects the performance of the play.

More Info: en.wikipedia.org