The Italian for ‘beautiful singing’ is used to describe Italian opera of the first part of the 19th century. Three pre-eminent Italian composers of that era are Rossini, Donizetti and Bellini. Bel canto also describes a style of singing that is associated with beautiful melodies, silvery voices and floods of rapid notes curling their way up and down the scale. Tenors and sopranos who sing bel canto tend to have lighter voices than those who sing, say, Verdi and Puccini. Bel canto voices also need a lot of flexibility to sing all those fast notes.
Opera exists to tell stories. What they do, though, is tell stories through music, specifically through the voices that sing it. Bel canto puts the full spotlight on the voices, which have a visceral effect in a way no other art form quite does. If you want to understand what makes opera special, and exciting to the people who love it, bel canto is not a bad place to start.