Opera buffa
Although we use the term “opera buffa” today, in the 18th century they called such operas by other names, e.g. “commedia in musica”, “dramma giocosa”, “operetta”, “burlesca” etc.  An opera buffa was usually a full length work: one which would fill a whole evening’s entertainment.  It was different from an “intermezzo” or “farsa” which was a short musical comedy that was performed during the intervals of a musical tragedy, although the difference between the two is not always obvious.  The intermezzo became longer and longer during the 18th century and gradually developed into opera buffa.  Pergolesi’s La Serva Padrone was an intermezzo which became very famous after Pergolesi’s death.  It influenced opera buffa.