Media Glossary : Breaking the Fourth Wall...

The fourth wall is an imaginary "wall", it was first established by live theatre and has been adapted for film and TV. In theatre a three-walled box set in a proscenium theatre through which the audience can see the action of the world in the play. The idea of the fourth wall was made explicit by Denis Diderot, it spread within the 19th century threat with the advent of theatrical realism, this extended the ideas to the imaginary boundary between fictional work and its audience. Shakespeare would often break the fourth wall, but it was also present during Ancient Greek theatre.
Within film and TV to "break the fourth wall" means speaking directly to the audience through the camera, it is a considered a technique of meta fiction as it deconstructs the boundaries normally set up by works of fiction. When a character breaks the fourth wall it means that they have acknowledged their fictionally either indirectly or directly addressing the audience, it can also be seen by the character interacting with their creator (this is more indirectly breaking the fourth wall however). To "break the fourth wall" successfully is difficult and is not used by many directors however there is a few example where it has been successfully used as a technique.

Example One:
+ Title = Kiss Kiss Bang Bang
+ Director = Shane Black
+ Date = 2005
+ Genre = Action/Comedy/Crime/Thriller
+ How it breaks the fourth wall = The entire film is narrated by the protagonist (who is played by Robert Downey Jr.), who breaks the fourth wall nearly every time he speaks
+ Trailer of Film =

Example Two:

+ Title = Ferris Buller's Day Off

+ Director = John Hughes

+ Date = 1986

+ Genre = Comedy

+ How it breaks the fourth wall = Ferris talks directly to the audience (even scolding them for staying until the end of the movie when the credits have finished)

+ Trailer of Film =