180 degree rule

                                                                              180 degree rule    

The 180 degree is where there's an invisible line and the camera stays on one side between to characters and this makes it look like there both facing the same direction.

The 180 degree rule is used a lot in films when there's a conversation going on this technique is used to make it look like two characters on screen are looking straight at each other to give the scene a more realistic look. This technique also pulls the audience in and engages the audience into the conversation.  

The 180 degree rule can also be broken this is done to show a emotional shift in the conversation between characters here are some examples of the rule being broken.

     Here's an example of how the 180 degree rule is used and how it can be broken:180 degree rule