A proscenium it can be said that it's a "window" that frames the play taking place on the stage. This type of stage, gives everyone in the audience a good view because the performers need only focus on one direction rather than continually moving around the stage to give a good view from all sides.
A thrust theatre stage is known by its arrangement which consists of being surrounded by audience on three sides. The Fourth side serves as the background.
Often the playing area is of square or rectangular shape