Answer: It is called "Soliloquy"
Explanation: A soliloquy is a popular literary device that is often used to reveal the innermost thoughts of a character. Soliloquy is derived from Latin word so meaning "to himself". It is a great technique used to convey the progress of of action of the play by means of expressing character's thoughts about a certain character or past, present, or upcoming event while talking to himself without acknowledging the presence of any other person.