The 180 degree rule is a guideline in film making where the camera is expected not to "cross" as it shows two characters in the samew scence should have the same left/right relationship with each other regarding their positioning.
If a camera is seen to pass over the "180 degree boundary" during an edit, it is known as "crossing the line." A shot taken from the opposite side is known as a reverse angle. Link: 180 degree rule - Moviemaking Techniques.
Shot Reverse Shot
Shot reverse shot is used as a very clever film technique to show one character looking at another character and back again, where the viewer assumes the action is direct.
Shot reverse shot is usually used whe filming dialogue. This is because we can fully capture the speakers action and the listeners reaction to what is being said.
Link: Shot Reverse Shot example.
Match on Action
Match on Action is a continuity editing technique. It is when something (an action) is happening in the scene and a cut is made, whilst the same piece of action is going on. It tends to connect different views of the same action at the same time.
Link: Match on action example.
