Short fiction is simply a short fictional story. Generally a short story is one that is written in the narrative format, with no more than 20,000 words, and no less than 1,000 words. Any type of story more than 20,000 words is considered a regular length story, while a short fiction story with less than 1,000 words would be considered a "short short story", or a work of "flash fiction".
In order to write a piece of short fiction, you will first want to think about the type of story you would like to write. Most authors come up with a general plot -- the beginning and the end, and then fill in the middle and other sections as they go along. Consider a short fiction story to be a condensed version, which means that you'll have to speed up the areas between the beginning, the middle, and the end. Concentrate on connecting the three together, and remember to keep your short fiction story under 20,000 words. If you find that you are unable to keep it under 20,000 words, consider changing your plot, or even one or two of the characters in the story. Making little changes to your story's outline can definitely alter its overall length.
Fiction Online