A ‘Drabble’ is a 100 word story, generally science fiction.
Like a Haiku, the best Drabbles have a twist at the end. The best way to approach writing a Drabble is to write a longer story, with the usual beginning, middle and end and pare it down (with a cleaver rather than a filleting knife). And finally, invest in (or bookmark) a thesaurus. It will help you to reduce your word count and yet allow you to say so much more.