An oratorio is a large musical composition for orchestra, choir, and soloists, according to The Other Wiki. Like an opera, an oratorio has recognizable characters, and is similar in length. Oratorios also tell a story. But unlike operas, oratorios are strictly concert pieces, with no props or costumes.

Oratorios are usually religious in nature, telling a story from the Bible or a saint's legend. The form was invented to keep the opera singers employed during Lent, when the theatres were closed down.

Oratorios are also similar to cantatas, in that cantatas are also large-scale vocal works and occasionally identifiable characters, but they usually do not tell a story (Bach's Coffee Cantata is a notable exception).

The best known oratorio is George Frederic Handel's Messiah (the source of the famous Hallelujah chorus), though J.S. Bach's two extant oratorios, the St. Matthew Passion and the St. John Passion, are also well-known.