The 180 degree rule is a very important concept in video and film production. It refers to an imaginary line which cuts through the middle of the scene, from side to side with respect to the camera. Crossing the line changes the viewer's perspective in such a way that it may cause disorientation and confusion. For this reason, crossing the line is usually something to be avoided.
Match on match
The cut between these two shots show that no time has passed between them. “Match on action” is when you cut during an action to another camera angle but showing the action from the same point in time that you left it from the previous shot. This is important to continue the flow of the scene.
A shot-reverse-shot sequence is the normal way of representing a conversation between two people.
The shots are taken from one participant‘s point of view, usually over the shoulder, then next shot is taken from the other participant's point of view.
The reasons for this convention are because taking a long take of a two shot might easily become tedious.
In editing, continuity is the process of disguising the construction of a scene by making it appear to ‘flow’ as if in real life. The 180 degree rule and match on match editing are crucial to this. The careful timing of cuts and transitions emphasizes the smooth shift of time and space. As long as continuity rules are followed, the plot and story can unfold in such a way that the audience can assume what happens in between shots.