This category of Storytelling Element is, in sum, what your story is built out of. The beginning, middle, and end - the elements that your reader can point to and say, "this scene is where the climax is," or "this was the primary conflict of the piece."
Not all of the Whats in this category are strictly necessary, but in general you'll need some of them to make the story make sense - after all, a brick building with no bricks is no building at all. A story with no introduction, no tension, no climax and no ending is hardly a story.
It's not always so clear-cut as all that, but we try. :)
To the next Element