From The Art and Popular Culture Encyclopedia
A theater or theatre (also a playhouse) is a structure where theatrical works or plays are performed or other performances such as musical concerts may be given. While a theater is not required for performance (as in environmental theater or street theater), a theater serves to define the acting and audience spaces and organize the theater space as well as provide facilities for the performers, the technical crew and the audience.
There are as many types of theaters as there are types of performance. Theaters may be built specifically for a certain types of productions, they may serve for more general performance needs or they may be adapted or converted for use as a theater. They may range from open-air amphitheaters to ornate, cathedral-like structures to simple, undecorated rooms or black box theaters. Some theaters may have a fixed acting area (in most theaters this is known as the stage), while some theaters such as black box theaters, may not, allowing the director and designers to construct an acting area suitable for the production.