Well, several things can make a story very short. Maybe it skips background details and goes straight to the main event. Or it could use concise language and avoid complex descriptions. Also, having a narrow scope and not exploring multiple subplots helps keep it short.
The characteristics of a very very very short story include simplicity. It doesn't have complex plotlines or numerous characters. For example, 'Bird flew. Sky was blue.' Also, it can be highly suggestive. Since it's so short, it makes the reader think more. Like 'Light went out. Silence.' It makes you wonder why the light went out and what the silence means. These stories are often about capturing a moment or a basic human experience in the most minimal way.
Sensual descriptions. For example, describing the touch of a lover's hand on the skin, like 'His fingers traced a slow path down her bare arm, sending shivers through her.' Also, the use of body language and eye contact. When two characters look at each other with a smoldering gaze, it adds to the sexiness.
A very very short story is marked by its extreme brevity. It usually doesn't have elaborate settings or complex subplots. Instead, it aims to convey a core idea or feeling quickly and effectively.
Once upon a time, a boy found a key. He opened a door and saw a magical world.
A very very very short story usually has only a few key elements and a simple plot. It might focus on one event or a brief moment without much elaboration.
A character and an action. For example, a boy ran.
A very short Hemingway story is often marked by simplicity and raw emotion. He has a way of cutting to the core of a situation with minimal words.
There was a cat. It chased a mouse. The mouse escaped.
A very short story is often referred to as a 'flash fiction'.
One short Christmas story could be: A child lost a toy on Christmas Eve but found it again with the help of Santa.