This play is a fictional play within a play, and it's a crucial plot device in Shakespeare's *Hamlet*.
Here's why Hamlet chose this play:
* To test Claudius: Hamlet suspects Claudius of murdering his father and wants to see his reaction to a play mirroring the circumstances of his father's death.
* To expose Claudius's guilt: The play is designed to trigger Claudius's guilty conscience and expose him in front of the court.
The play itself is a short, violent drama depicting a king being poisoned while sleeping. The play serves as a key turning point in *Hamlet*, leading to Claudius's confession and eventually, his downfall.