In film making, the 180-Degree Rule is a basic guideline regarding the on-screen locational relationship between multiple characters in a scene. An imaginary line called the axis divides the camera from the actors. All shots in the scene should be executed on the same side so that the audience can understand where characters are specially to each other. The camera needs to remain on the same side of the scene in a camera arch not greater than 90 degrees. In other words, an actor on the left needs to stay on the left and the actor on the right needs to stay on the right. Otherwise, if a later shot is on the opposite side of the characters where they switch sides then the viewer/audience becomes disoriented. To break the axis is called jumping the line or crossing the line.
The exceptions would be if you displayed a buffer shot which was right on the line so that the audience can adjust. Another exception would be if you have a shot that crossed over the line during the dialogue or action. For example, if you a handheld shot rotated around the scene.