I used to have a teacher who said this as well. The best way to understand would be to show examples of how to specify such terms as “stuff” and “things”. For instance: “The birds have lots of stuff.” That was not clear because the reader does not know what the “stuff” is. Instead, the text could be changed to: “The birds have lots of feathers.” Now the reader knows what the stuff is because it has been replaced with a more specific word. If you go over multiple examples in your head, it will become easier to comprehend and you will get used to doing it.
All of these plus the likes of shadow beams of moonlight
that illuminate the castle through the broken roof or a window and extreme landscapes
with passion driven characters are all the elements of Gothic literature. Main
characteristics of the Gothic atmosphere are mystery, gloom and suspense which
all contribute to the recognizable chilly atmosphere.