180° rule
In film making the 180-degree rule is one of the fundamental
and basic guidelines 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 will always be
frame right of the second character, who is then always frame left of the
first. If the camera passes over the axis, it is called crossing the line or
jumping the line.
this video help explain what the 180 rule is.
