The 180-degree rule in filmmaking establishes an imaginary line called the axis between characters or objects in a scene, and recommends keeping the camera on one side of this line in every shot so the characters' positions remain consistent from the audience's perspective. Crossing this axis by moving the camera to the other side could disorient viewers by changing which side a character appears on screen from shot to shot.

1. 180 Degree Rule

2. In film making, the 180-degree rule is a basic guideline
regarding the on-screen spatial relationship 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 this axis for
every shot in the scene, the first character will always be
frame right of the second character, who is then always
frame left of the first. If the camera passes over the
axis, it is called jumping the line or crossing the line.

4. For example; In a dialogue scene between two
characters, the camera may be placed anywhere on
the green 180° arc and the spatial relationship
between the two characters will be consistent from
shot to shot, even when one of the characters is not
on screen. Shifting to the other side of the
characters on a cut, may disorient the audience.

5. Here is an example of the 180 Degree Rule in action...