A very common fictional concept is that the characters are unaware of the fact that they are characters in somebody else's work of fiction.
This separation between the characters' world and the audience is the Fourth Wall — named for the imaginary wall at the front of a stage play beyond which the actors are (usually) not supposed to cross. It's an Omnipresent Trope, because the separation of fiction and audience helps preserve the latter's Willing Suspension of Disbelief: The fictional characters treat their story as Real Life, and audience interprets it the same way. See Three-Wall Set for the production implications of this concept; for example, The Couch often directly faces the Fourth Wall. The exploration and subversion of the Fourth Wall is a common trait of Post Modernism.
No examples, please; this merely defines the term. Straight uses of the Fourth Wall are far too numerous and trivial to list, compared to examples of Breaking the Fourth Wall or when there is No Fourth Wall.
- Addressing the Player: Talking to the player in a video game
- Aside Comment: A line directed to the audience and apparently not heard by other characters, as if the speaking character is thinking aloud
- Aside Glance: Someone casts a look in the direction of the audience or screen (usually as reaction to what's happening), doesn't say anything, and doesn't get acknowledged.
- Audience? What Audience?: Someone mentions something that implies the work is fictional (like writers, an audience, etc) and another person is just confused.
- Breaking the Fourth Wall: Characters talking directly to the audience through the wall of the set that's missing because the audience or camera are there, but is still assumed to exist. Also used more broadly to mean acknowledging that their world is a fiction and they are performers within it.
- Breaking the Reviewer's Wall: Reviewers interacting with the work's characters.
- Camera Abuse: Something affects the camera so that the screen will appear wonky.
- End-of-Series Awareness: A character is aware they're fictional and that their work is ending.
- Exploiting the Fourth Wall: Using the fourth wall for practical reasons.
- Found Footage Films: Putting the camera on the character's side of the fourth wall.
- Fourth-Wall Mail Slot: Fictional characters answer questions from the real viewers/readers/etc.
- Fourth Wall Myopia: Where fans forget that fictional people won't know as much as their watchers do.
- Fourth-Wall Observer: One person is aware the work is fictional.
- Fourth-Wall Portrait: In a work with cartoony-looking people, someone thinks a realistic drawing of a person looks crazy.
- Fourth Wall Psych: The fourth wall appears to be broken but isn't really.
- Fourth Wall Shut-In Story: An author gets trapped in their own work.
- The Fourth Wall Will Not Protect You: Implications that the fictional danger will affect the audience, such as the villain acting like they're going to hurt/kill/etc the viewers.
- Frame Break: Breaking through (or even just hitting) the frame of the panel.
- From Beyond the Fourth Wall: Someone in a work gets items from the author or us.
- Interactive Narrator: The characters interact with the narrator of the story.
- Leaning on the Fourth Wall: Acknowledging aspects of the fiction without quite being aware of it, such as saying things like "If this were a movie".
- Logging onto the Fourth Wall: Fictional websites.
- Medium Awareness: Beyond being aware of being fictional, characters know their story's format; marking time in "episodes" or "issues", knowing that everything happens over length of a TV show, etc.
- Ninja Prop: Props that should've been beyond the fourth wall suddenly affects the world in some way.
- No Fourth Wall: Everybody is well aware they're fictional characters.
- No Inner Fourth Wall: Characters in a Show Within a Show break their own fourth wall.
- Noticing the Fourth Wall: Characters suddenly realise they're fictional.
- Painting the Medium: Some part of the fiction is stylized to convey an information for the audience; this stylizing won't be noticeable to the fictional characters themselves.
- The Player Is the Most Important Resource: Video game characters state that they need the players.
- Prop: Something an actor holds or physically interacts with in a production.
- Reaching Through the Fourth Wall: The characters, objects, or concepts in non-physical realities move across the story-device boundary and become physical non-animated characters or objects to apply.
- Reading Ahead in the Script: The characters predict the future by reading their script.
- Refugee from TV Land: Someone goes through the fourth wall and enters the land of reality.
- Scolding the Fourth-Wall Breaker: A character scolds another character in-universe for breaking the fourth wall.
- Screen Tap: Tapping the screen.
- Sliding Scale of Fourth Wall Hardness: There are gradations of how much of a break some of these others can be; for example, an Aside Comment can just be a character thinking on the "harder" side, while adding in some Medium Awareness into your Aside ("She'll run out of the room now, I just know it" vs. "She'll run off stage now, I just know it.")
- Stop Poking Me!: Characters in a video game tell the player to stop poking them with the cursor.
- This Is Reality: "That only works in a movie" say the characters in a movie.
- Trapped in TV Land: Someone goes through the fourth wall and enters the land of fiction.