The 180 degree rule, this way of filming helps to maintain continuity. To understand the 180 degree rule you can imagine a circle around your characters and have a line going through the centre of them, if you wanted to film them talking to one another you must say on one side of this circle because you want to ensure that one character is always on the right and the other will always stay on the left, this will also keep there eyesight in the same direction no matter where you stand in that half of the circle.
(This picture i have uploaded from google images)
The picture above helps to understand my explanation of the 180 degree rule and how you must stay on one said of the circle because as shown the blue person is on the right in the picture where they have decided to film (the green half) and when they filmed on the opposite side the person in blue ends up on the left. For these reasons it is important to stick to the 180 degree rule.
Shot reverse shot is an editing technique that is most commonly used in conversations. To create this effect you will film the first person then edit a clean cut across to the second person then again cut across back to the first person.
