The classic stage: a picture frame at one end of the room, with the audience facing it.
A proscenium stage sits behind a large arch or frame, with all of the audience in front. It is what most people picture when they think of a theater, and it makes big scenery and quick scene changes easy because everything can be hidden behind and above the frame.
Also seen as: proscenium stage, proscenium arch, proscenium theater