A libretto is the text or script of an opera, musical, or other vocal work. It includes the lyrics sung by the performers and the spoken dialogue, providing the narrative and emotional context for the music. The term comes from the Italian word for "little book," reflecting its role as a companion to the musical score. In addition to operas, a libretto can also be found in other forms of musical theater, such as musicals and operettas. The collaboration between the librettist, who writes the libretto, and the composer is crucial for creating a cohesive and engaging performance.