What is the chorus function in the play?

What is the chorus function in the play?
In ancient Greek plays, the chorus played an important part in the telling of the story. They were considered the narrator of the play, and often sang songs between speeches and continued the story between scenes.

In modern American musicals, the chorus usually functions as the "choir." Singing large songs, act openings and closing, moving the story forward, and singing backup for the principals.

In some ways, the chorus hasn't changed much since the ancient Greek days!