What is a word that describes the class that "background" and "foreground" are members of?

What is a word that describes the class that "background" and "foreground"
are members of?

If I say
"It was happening in the foreground."
or
"It was happening in the background."
"Foreground" and "background" are examples of locations in some kind of
metaphorical space, regardless of what they are foreground or background
of. Is there a good word for these sort of "locations" in the abstract,
without regard to the medium (visual arts, music, theater, etc) that the
foreground and background exist in?