How is play within a play used?

Play within a play is a theatrical device where a secondary play is performed within the main play, serving various purposes such as enhancing themes, providing commentary, or advancing the plot. It allows characters to reflect on their own situations, often revealing truths or hidden emotions. This technique can create layers of meaning and engage the audience in a deeper exploration of the narrative. A notable example is found in Shakespeare's "Hamlet," where the play "The Mousetrap" highlights themes of guilt and deception.