The 180 degree rule
Referred to as the line (as in "that will cross the line") or, less commonly, "the axis"
Helps orient the audience
A scene can have multiple, or changing lines
Requires constant awareness of the actors' eyelines (left or right)
Cross the line INTENTIONALLY for effect
Straight into the lens for direct address or dramatic effect (unusual)
Multiple characters
*Remember:
Left = Camera/screen left
Right = Camera/screen Right