The 180 degree rule

This rule means that when filming people having a conversation the camera should stay on one side of them so each time you change shot direction each character is facing each other. This ensures continuity between shots. I have used an image from google to explain the 180 degree rule. The camera must stay within the semi circle to the side of both characters that are having the conversation, if the rule is broken it appears that the characters are not looking at each other.

Shot reverse shot

Shot reverse shot is a camera angle showing a conversation between two characters. The camera cuts between each character. The shots should clearly show the characters looking at each other. The image below shows a shot reverse shot. 

Below is a video we made which demonstrates the 180 degree rule and shot reverse shot.