an = at
an der Wand = at the wall
an der Tür = at the door
in = in/into
in dem (masculin & neutrum Dativ) = im = in the
in das (neutrum Akkusativ) = into
****** Ort {m} = Place ******
in Deutschland
im Auto {n}
im Kino {n}
im Supermarkt {m}
in der Schule {f} = in the school
im Süden {m} = in the South
im Haus {n} = in the house
****** Richtung {f} = direction ******
in den Supermarkt {m} = into the supermarket
ins Kino {n} = into the cinema
in die Schule {f} = to school / into the school
ins Internet {n} (yep, we gain access to the magic cyberworld like in those fancy 80s movies and we surf "in" the internet, not "on")