The 180 degree rule in film establishes the positions of characters in a scene so that the viewer is not disoriented. It dictates that the camera must stay on one side of an imaginary line between any two subjects, so their left/right positions remain consistent. Breaking this rule by crossing to the other side of the line during an edit can confuse viewers about which direction the characters are facing. The rule is important for clearly conveying who is who during dialogue scenes between multiple people.