Continuity editing is also very popularly known as the type of editing classically used in Hollywood films, and was developed by early European and American directors, a good example of which being D.W. Griffith, and his films such as The Birth Of A Nation. A filmmaker would use them as it makes the film a lot easier for the film to follow, and thus makes it more enjoyable. It uses techniques such as the 180 degree rule, which basically states that two characters (or other objects) in the same scene should always remain in the same left/right relationship to each other, this is so the characters/objects don't appear to have swapped positions on screen. If the camera passes over the imaginary axis created, and shows the two characters/objects to have switched positions, it is known as crossing the line.
The second technique that is embodied in continuity editing is known as Match on Action, a technique used to link two shots together. In this, we see a character start performing an action in the first shot, and continuing or finishing said action from a completely different angle in a new shot. The use of this technique makes the action seem like natural and realistic movement, whereas in reality, the actor may have had to perform it twice. A good example of this would be in "Star Wars: A New Hope", the following scene shows Old Ben Kenobi examining an unconscious Luke Skywalker, the scene consists of 3 different angled shots, and seems to flow very smoothly.
The third technique is called Shot, Reverse Shot. Much like the previous two techniques, this is also used to link two shots together. The first shot is used to reveal the first character of the scene, which is followed by the second character being revealed in the second shot from a different angle. This is used to allow the audience to connect the two characters, and they can see that they are interacting with each other, even though their scenes may have been recorded seperately, and edited together, to make it seem like they were actually facing each other and interacting.
The fourth and final technique is known as Eye-line Match, and again, is used to link two shots together. The first shot will show the character looking at something out of the audiences view, it then changes shot to show what the character was looking at. This is used to allow the audience to feel like they're experiencing what the characters on screen are experiencing.
