Sentence:  This creates a separation of the three worlds: three because, apart from the 'real' world of the audience and the perceiving minds of individual spectators, the one on the stage is in fact dual in nature, material and fictional, with both spheres divided by the <WSD>fifth wall</WSD>. 
Meaning of the word marked with <WSD> tags:  The division between the fictional world depicted, and the actual actors, props, etc.