In theatre, the stage is a designated space for the performance of theatrical productions. The stage serves as a space for actors or performers and a focal point for the members of the audience. As an architectural feature, the stage may consist of a platform or series of platforms. In some cases, these may be temporary or adjustable but in theatres and other buildings devoted to such productions, the stage is often a permanent feature.
Since the Italian Renaissance, the most common stage used in the West has been the proscenium stage which may also be referred to as a picture frame stage. The primary feature is a large opening known as the proscenium arch through which the audience views the performance. The audience directly faces the stage which is typically raised several feet above front row audience level and views only one side of the scene. This one side is commonly known as the invisible fourth wall of the scene. The proscenium arch evolved from the proskenium in Ancient Greek theatres. This was the space in front of the skênê or backdrop where the actors actually played. The first indoor theatres were created in French tennis courts and Italian Renaissance palaces where the newly-embraced principles of perspective allowed designers to create stunning vistas with buildings and trees decreasing in size toward a "vanishing point" on the horizon. Stage floors were raked upward slightly from front to back in order to contribute to the perspective illusion and also to make actors more visible to audiences, who were seated on level floors. Subsequently, audience seating was raked, and balconies were added to give audiences a fuller view. By the end of the 19th century most stages had level floors, and much of the audience looked down on, rather than up to, the stage.
The competition among royals to produce elegant and elaborate entertainments fueled and financed the expansion of European court theatres. The proscenium which often was extremely decorative in the manner of a triumphal arch "framed" the prospective picture. The desire of court painters to show more than one of their perspective backgrounds led court architects to adapt the pin-rails and pulleys of sailing ships to the unrolling, and later to the lowering and raising, of canvas backdrops. A wood (and later steel) grid above the stage supported pulleys from which wooden battens, and later steel pipes, rolled down, or descended, with attached scenery pieces. The weight of heavy pieces was counterbalanced by sandbags. This system required the creation of a storage stage house or loft that was usually as high or higher than the proscenium itself. A "full-fly" stage could store the entire height of scenery above the visible stage using the pin-rails before or during performance, whereas a "half-fly" stage (common in smaller locations) could only store props of limited size and thus required more careful backdrop and scenery design. Theatres using these rope systems, which are manually operated by stage hands, are known as hemp houses. They have been largely supplanted by counterweight fly systems.
The proscenium, in conjunction with stage curtains called legs, conceals the sides of the stage, which are known as the wings. The wings may be used by theatre personnel during performances and as storage spaces for scenery and theatrical properties. Several rows of short curtains across the top of the stage, called teasers, hide the backdrops, which in turn are hidden above the stage in the fly system loft until ready for use. Often, a stage may extend in front of the proscenium arch which offers additional playing area to the actors. This area is a referred to as the apron. Underneath and in front of the apron is sometimes an orchestra pit which is used by musicians during musicals and operas. The orchestra pit may sometimes be covered and used as an additional playing space in order to bring the actors closer to the audience. The stage is often raised higher than the audience. Space above some proscenium stages may include a flyloft where curtains, scenery, and battens supporting a variety of lighting instruments may hang. The numerous advantages of the proscenium stage have led to its popularity in the West. Many theatrical properties and scenery may be utilized. Backdrops, curtains and lighting can be used to greater effect without risk of rigging being visible to the audience. Entrances and exits can be made more graceful; surprise becomes possible. The actors only have to concentrate on playing to the audience in one direction. The one downfall to a proscenium stage is that it is difficult (though not impossible) to turn it into something else.