Romantic opéra was Italian Opéra. The phrase grand opéra implied the French recitative opéra. But since the 18th century, it was considered conservative French works during the Romantic period.
Opera began at the end of the 16th century in Florence, Italy. Opera was invented by a group of amateur poets and musicians who were trying to recreate the art of Greek drama. The members of the group included Vincenzo Galillei, whose father was Galileo, the scientist.
During this period, ballet, comedies, and masque which included music and dance.
In the 19th century, almost all of the operas were tragic. In contrast, operetta was created to express the lighter side of drama. The difference between opera and operetta is, when an Opera is performed, every song is sung. In an operetta, there is some acting combined with songs.