Prose craft
Aside
A dramatic device in which a character speaks to the audience, by convention unheard by the other characters; usually brief rather than a full speech.
An aside is "a dramatic device in which a character speaks to the audience." By convention the audience understands that the other characters on stage cannot hear the speech; it may be spoken directly to the audience, in or out of character, or represent an unspoken inner thought. It is "usually a brief comment rather than a speech, such as a monologue or soliloquy." The article's modern masters are television's direct addressors: Francis Urquhart in the BBC's House of Cards (1990), Frank Underwood in the Netflix remake, and the leads of Chewing Gum and Fleabag.
In prose the aside is a deliberate crack in the fourth wall: a narrator or character suddenly talking to the reader over the story's head. Used once it sharpens a monologue or a deadpan comic voice; used constantly it burns the distance the story runs on. Web serials park the impulse in the author's note, outside the chapter proper.