180 Degree Rule

180 Degree Rule is described as below:
In a dialogue scene between two characters, Justin (orange shirt, frame left in the diagram) and Drew (blue shirt, frame right), 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 character is not on screen. Shifting to the other side of the characters on a cut, so that Drew is now on the left side and Justin is on the right, may disorient the audience.

However if the 180 degree rule is crossed, it will confuse the audience because the directions will be different. For example if we see a person on our left and then suddenly they change directions and we see them on our right, it will confuse us as we will be wondering if the person was on the right or the left.