1. Advance the plot: The play-within-the-play, "Pyramus and Thisbe", is used as a way to move the plot of _A Dream_ forward, as it allows for the characters to discuss the events of the main play and their relationships to one another.
2. Convey themes and ideas: The play-within-the-play is used to explore the themes of the play, such as the nature of love, the power of imagination, and the consequences of one's actions, amongst others.
3. Create humor and entertainment: The play-within-the-play provides comic relief and entertains the characters within _A Dream_ as well as the audience, as it features humorous elements such as the over-the-top acting and the ridiculous misunderstandings.
4. Mirror and parallel events in the main play: The play-within-the-play mirrors and parallels events that are happening within the main play, creating a layering effect and exploring the themes and ideas of _A Dream_ in a deeper and more nuanced manner.
5. Serve as a commentary: The play-within-the-play is used as a commentary on the nature of theater, art, and the role of acting and performance, as well as the artifice and constructed nature of the performance.