180 Degree rule

In film making, the 180-degree rule is a basic guideline regarding the on-screen spatial relationship between a character and another character or object within a scene. An imaginary line called the axis connects the characters, and by keeping the camera on one side of this axis for every shot in the scene, the first character is always frame right of the second character, who is then always frame left of the first. The camera passing over the axis is called jumping the line or crossing the line.

The object that is being filmed must always remain in the center, while the camera must always face towards the object.

The 180 degree isn't a static rule in the sense that we could break it without the world ending however to break this rule it is important that we as a group understanding what we are doing otherwise our audience will be left confused.

For example this rule is best explained through a conversation between two characters because they are looking at eachother. If I wanted to shoot this from a wide angle then two close ups I would have to create an imaginary line that cuts through the middle of the scene because this line is where the camera is advised not to cross.
The reason behind this because if I was to cross the line within the same scene then the actors would look like they were facing the same way and seem like a flipped image. The reason this is further a problem is because it ruins the eyeline match.