What is it? and how do I write it well?
Flash fiction is a medium of brief stories which can range in length from 5 -2000 words. These stories, unlike short stories, often don't focus on characters or plot, rather emphasising movement. If a line doesn't reveal more about a character or progress the story then it probably doesn't belong in these stories.

Flash fiction stories manage to contain a beginning, middle, end, character development and descriptions all within a miniature world. There are several categories for flash fiction depending on the word count. For example, flash fiction often has a max word count of 1500; sudden fiction has a max of 750; a drabble has a max word count of 100 words, whilst a dribble is often 50 words.
How do I write them?
Whilst it is important to make sure you tell a story within your writing, there are several tips you can use when writing flash fictions works.
1. Try starting in the middle - its not for everyone but you certainly don't have time (well, words) to build characters and form sets.
2. Make your last line count - ensure that the last line is not the end, it should take the reader to a new place (much like the beginning of a new story).
3. Write lots, then cut down - write as much as you want, then trim it down to the bits that matter within the story.
4. Keep it simple - cut out any unnecessary characters, dialogue and descriptions.
Good Luck!