Stairs will lead into the other set of stairs that share a number
Green lines signify a switch
Blue and orange signify art
Black/gray figures and black lines signify that you cannot pass (the brown wavy lines too, I won't spoil what they are)
The Red and orange figures and the bell by the save point signify npcs.
Light blue lines just take you to where they are pointing.
Ignore the black arrows on the tiles on the left side of the map, those were errors in pathing that have since been fixed last I heard.

Hope this helps, don't forget to feel, scream and smell.