I was naive when I was in college. I knew that writing a book would be different than writing a short story. I mean the book is much longer. You add some words, throw in some tangents to go off on and BAMMO- you have a book.
I have learned a lot since then. For one I learned that the short story and its close cousin, the flash story, are completely different beasts than a novel. Aside from the obvious length. You have to think about different things to make them work.
The flash is, in my opinion, the story at its most elegant. It is petite and to the point. A slice of life. It is the prose equivalent of a poem.
The short story tends to ramble a little more, still without a word out of place in it best case. We get to know the characters and perhaps the setting a little more. We have a larger world to explore within the short story.
The novel. What can I say about the novel and its step-brother, the novella. At least from a writers point of view. We have not only a world we can explore, but universes. We get the chance to play God on a grand scale. With no limits to how we do it and how long we take for the journey, as long as we hold the readers and our own attention long enough to make it work.
I find it unfortunate that the university setting that I was educated in, at least in my writing classes, focused on the short story exclusively. Not that I didn't get a good education. I wasn't ready to play God at that point either. Something about walking before running. (I wasn't very good at the flash story at that point either.)