Hamlet is speaking to some actors about putting on a play. Hamlet would like this play to re-enact his fathers death. He does this in order to confirm his knowledge of Claudius killing the Late King Hamlet.
Thank goodness no one knows I killed my brother!
Hamlet's plan is beginning to work. Claudius is getting itchy, nervous and can't sit still for his life. Hamlet sees this and tells the actors to carry on to the next scene.
Lights! Lights! Stop this play at once!
In this scene Hamlet tells the actors to show the fallen king's wife becoming now married to the king's brother and murderer thus giving him complete power of Denmark and showing this horrendous act of incest.
This scene depicts Claudius' coronation and therefore coming near to the end of the play. By now Claudius is trying to make the play finish due to his uncomfortableness with the reality of this subject.
Finally, Claudius has had enough he stands up and declares the play be stopped.
The play has now finished and Hamlet's information has been declared true.