An oratorio is a large musical composition for orchestra, choir, and soloists. It typically tells a religious story and is performed in concert settings rather than staged like an opera. Oratorios often include recitatives, arias, and choruses, allowing for a variety of musical expressions. The most famous oratorio is George Frideric Handel's "Messiah," which is frequently performed during the Christmas season. Oratorios emerged in the 17th century and became popular in the Baroque period, with composers like J.S. Bach and Haydn contributing significantly to the genre.