The term proscenium refers to a large arch or opening that is often used in theater productions. It is the frame or wall that separates the stage from the audience, and it usually includes an ornamental design at its top edge. The purpose of the proscenium is to create a clear separation between the action taking place on the stage and the viewing area for the audience. In ancient Greek theaters, the term "proskenion" was used to describe the raised platform where actors performed, and it is from this origin that we derive our modern-day understanding of what proscenium means in a theatrical context.