What is the subject of the hamlets second soliloquy, the famous "to be or not speech?

In Hamlet's second soliloquy (II. ii. 560-617), he reacts to a speech that has just been delivered by one of a travelling group of players, or actors, recently arrived at the castle. This speech concerns the ancient tale of the fall of Troy at the hands of the Greeks, and the tragic murder of the Trojan king, Priam. The Player appears to be overcome by the emotion of the scene, and ends up with tears in his eyes as ...