Final answer:
The style of opera popularized by Gioachino Rossini is called Bel Canto, known for its vocal beauty and agility, marking a shift from the more ornate Baroque style.
Step-by-step explanation:
The style of opera popularized by Gioachino Rossini is called Bel Canto, which literally means 'beautiful singing' in Italian. Rossini, along with other composers like Vincenzo Bellini and Gaetano Donizetti, was a leading figure in this style during the early to mid-19th century.
Bel Canto is characterized by its emphasis on vocal technique, the beauty of the human voice, and expressive agility, which was contrary to the more theatrical and ornate style of the Baroque era that preceded it. Rossini's operas are marked by their brilliant vocal lines, crisp articulation, and a more direct dramatic expression.