thrust

In theater, a thrust stage (also known as a platform stage or open stage) is one that extends into the audience on three sides and is connected to the backstage area by its up stage end. A thrust has the benefit of greater intimacy between performers and the audience than a proscenium, while retaining the utility of a backstage area. Entrances onto a thrust are most readily made from backstage, although some theatres provide for performers to enter through the audience using vomitory entrances. An arena, exposed on all sides to the audience, is without a backstage and relies entirely on entrances in the auditorium or from under the stage.