"Short" short stories are what makes up Flash Fiction--short stories usually told in less than 2,000 words. Some Flash fiction can be as short as 10-50 words, while other flash fiction genres are up to 2,000 words.
Websites for Writing Flash Fiction
What is Flash Fiction?
Flash fiction is micro fiction, short short stories told typically in fewer than 2000 words, though some consider flash fiction to be fewer than 1000 words. Flash fiction is also sometimes called: sudden fiction, micro fiction, micro short story, short short story.
Flash fiction differentiates itself from a vignette in that it has all the elements of a full story, including a main character (protagonist), a conflict (plot) and a resolution (ending), it just unfolds these things in very few words.
When calculating word count for a flash fiction piece, typically, the title is not included as part of the total word count. However, one should take care not to write a piece that is dependent upon the title for telling the story.