In drama, a speech delivered by a character that is heard by the audience but not by the other characters on stage is called

An aside is a brief remark made by a character that is intended for the audience and is conventionally understood to be inaudible to the other characters on stage. A soliloquy is a long speech in which a character speaks thoughts aloud when alone, a monologue is a long speech by one character, and a prologue is an introductory section of a play.