The 180 degree rule

In film making, the 180 degree rule is a basic guideline regarding the on-screen spatial relation between a character and another character or object within a scene. An imaginary line called the axis connects the characters, and by keeping the camera on one side of the axis for every shot in the scene, the first character, who is then always frame right of the second character, who is then always frame left of the first. The 180 degree rule enables the audience to visually connect with unseen movement happening around and behind the immediate subject and is important in the narration of battle scenes. If you break the rule intentionally, it disrupts the scene and disorients the audience meaning that when the 180 degree rule is broken; the person who was initially facing left in a scene is all of a sudden facing right.