Question

What term describes what an actor breaks when he addresses the audience directly from stage, like in Hamlet’s “to be or not to be” soliloquy?

Answer 1

the answer to this question is breaking of the fourth wall.
The fourth wall in a play refers to the figurative dimension that separates the audience and the character's in the play
When the actor addresses the audience as he played the character, he breaks this dimension and brought the audiences to directly become a part of the story.