The difference between e.g.
unten is depending on what you are referring to and positions to each other. So the difference between
unten is the same as in
under your foot and
down stairs. So as a rule of the thumb I'd say, when ever you putting something in relation to something else, it should be really the preposition
If something is at a position not really related to something, than it's
hinten. This also applies to positions inside e.g. a room: So you can say "Es befindet sich unten (im Keller)" means maybe something like "It's downstairs (inside the cellar)" whereas "Es ist hinter dem Keller" means "It's behind the cellar".
I have no clue how the grammatical thing is called ;)