The presence of an audience is an essential element in live performance. No two performances, or audiences, are identical. Each performance is unique: the audience's response varies according to the characteristics of its members; and the performance varies according to the audience's response, as well as to other factors affecting the actors.

A special member of the audience is the critic or the reviewer. The reviewer usually writes for a newspaper, a magazine, or television; he or she describes the theater event and gives an opinion as to its worthiness. The critic usually writes for a magazine or scholarly journal and describes and analyzes the event in greater detail and depth than the reviewer.

Criticism usually falls into one of two categories: descriptive, which explains what actually happened on a stage; or prescriptive, which creates rules for what ought to take place on a stage.