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 [[OmnipresentTropes Omnipresent Trope]], because the separation of fiction and audience helps preserve the latter's WillingSuspensionOfDisbelief: The fictional characters treat their story as RealLife, and audience interprets it the same way.
See ThreeWallSet for the production implications of this concept; for example, TheCouch often directly faces the Fourth Wall.
Straight uses of the Fourth Wall are ''far'' too numerous and trivial to list, compared to examples of BreakingTheFourthWall or when there is NoFourthWall.
The exploration and subversion of the Fourth Wall is a common trait of Post Modernism.
Not to be confused with [[WebVideo/AtopTheFourthWall That web show done by Linkara that reviews bad comic books.]]
Big list of related pages (overlaps somewhat with MetafictionDemandedThisIndex):
* AsideGlance: Someone looks in the direction of the screen, doesn't say anything, and doesn't get acknowledged.
* AudienceWhatAudience: Someone mentions something that implies the work is fictional (like writers, an audience, etc) and another person is just confused.
* BreakingTheFourthWall: Talking to the audience.
* BreakingTheReviewersWall: Reviewers interacting with the work's characters.
* CameraAbuse: Something affects the camera so that the screen will appear wonky.
* ExploitingTheFourthWall: Using the fourth wall for practical reasons.
* FoundFootageFilms: Putting the camera on the character's side of the fourth wall.
* FourthWallMailSlot: Fictional characters answer questions from the viewers/readers/etc.
* FourthWallMyopia: Where fans forget that fictional people won't know as much as their watchers do.
* FourthWallObserver: One person is aware the work is fictional.
* FourthWallPortrait: In a work with cartoony-looking people, someone thinks a realistic drawing of a person looks crazy.
* FourthWallPsych: The fourth wall appears to be broken but isn't really.
* FourthWallShutInStory: An author gets trapped in their own work.
* TheFourthWallWillNotProtectYou: The villain acts like they're going to hurt/kill/etc the viewers.
* FrameBreak: Breaking through (or even just hitting) the frame of the panel.
* FromBeyondTheFourthWall: Someone in a work gets items from the author or us.
* LeaningOnTheFourthWall: Implying the fourth wall or saying things like "If this were a movie".
* LoggingOntoTheFourthWall: Fictional websites.
* MediumAwareness: Being aware you're fictional.
* NinjaProp: Props that should've been beyond the fourth wall suddenly affects the world in some way.
* NoFourthWall: Everybody is well aware they're fictional characters.
* NoInnerFourthWall: Characters in a ShowWithinAShow break the fourth wall.
* NoticingTheFourthWall: Characters suddenly realise they're fictional.
* PaintingTheMedium: 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.
* ThePlayerIsTheMostImportantResource: Video game characters state that they need the players.
* ReadingAheadInTheScript: The characters predict the future by reading their script.
* RefugeeFromTVLand: Someone goes through the fourth wall and enters the land of reality.
* ScreenTap: Tapping the screen.
* ThisIsReality: Characters think they're real people.
* TrappedInTVLand: Someone goes through the fourth wall and enters the land of fiction.