The 180 Degree Rule:

 

The 180 degree rule applies to the movement and the angle posititioning on a camera. The 180 degree rule specifically focuses on keeping the camera in one particular view of action. The main principle of the 180 degree rule is that actors do not cross the imaginary line which separates the axis from the character(s) who is on screen at the time, and that they keep consistent continuity throughout. The 180 degree line is perpendicular to the cameras direction to establish a specific shot of the scene. The 180 degree rule prevents the audience from confusion, as the actors will be on the same side. The 180 degree rule is also a prevention of the audience feeling lost, and missing essential shots in the film. An example of the 180 degree rule is if two people are having a conversation and they are sitting opposite each other, the camera has to be on the same side as them and not cross the line which will result in them appearing on the wrong side.