What is the function of chorus in drama?
The role of the chorus in drama is much like the role of the narrator of a novel or story. The chorus provides some structure to the narrative and can provide information and commentary that need not be in the actors' lines. The chorus can also provide foreshadowing or humor. The chorus acts as a kind of liaison between the audience and the actors, giving the audience a lens through which to view the action of the drama, allowing the audience to identify with a group that is "outside" the action, the way a frame story operates, with a narrator telling a story within a story, giving the reader a narrative one step removed. This is an ancient technique in drama, for example, in Oedipus Rex. However, there are modern instances of the chorus. One example that comes to mind is Little Shop of Horrors, which uses a singing "chorus" to great effect, with narration and humorous commentary.
Classical drama, according to Aristotle, started as exclusively choral, in performances known as "dithyrambs". The addition of individual actors was a later development. Choruses are used differently in tragedy and comedy. They sometimes speak as normative voices, reminding the audience of shared standards being violated by the characters. At other times, they may add narrative elements.
In the actual staging of ancient tragedy, choruses, like those of modern opera, dance, adding impressive visual components to a drama.
In some plays choral odes are clearly connected to plot development, but in others they serve as poetic and visual interludes with only tenuous connections to the main plot.