Where is it? Good question. Now this is only my opinion. First off, we have North Hollywood, which in my view is basically everything south of Roscoe to Mulholland, more or less west to Coldwater Canyon (Fulton in some places) and east to the Burbank border. Now that does include some disputed territory for sure, but consider that the greater area this blog deals with.
More specifically there is the NoHo Arts District which traditionally has been Burbank Boulevard on the North, Camarillo Street on the South, Cahuenga Boulevard on the east and Tujunga on the West.
Now what is Downtown NoHo and in my view that is basically the area surrounding the Metro Red Line Station, Metro Orange Line Station and the Academy of Television Arts and Science complex. So more or less rough borders would be Magnolia on the south, Tujunga on the west, Cumpston on the north (and yes we know Cumpston has been closed to Vineland with the opening of East Valley High School, but you get the drift) and Vineland on the east. This takes in the Metro stations, NoHo Commons, Academy Plaza and a good chunk of the district theatres, etc.
But you may have a different view. Feel free to post it.