What does few-shot mean?
Few-shot means you put a small number of worked examples inside the prompt, each showing an input and the answer you would want for it, and then add your real request. The model reads the examples, picks up the pattern, and answers your request in the same shape. You taught it nothing permanent. The lesson lives entirely in the prompt and is gone the moment that prompt ends.
It is the middle ground between describing a task and demonstrating it. Some formats are awkward to spell out in words but obvious to show, and that is exactly where a couple of examples earn their place. Show the model two answers in the layout you want, and the third tends to match.
When are the examples worth their room?
Examples are not free. They sit in the context window alongside your real request, so they spend the same budget the model needs for the input and its answer. If a plain instruction already gets the result, the examples are dead weight, and zero-shot, no examples at all, is the cleaner choice.
There is a sharper catch: the model copies what you show it, flaws included. A sloppy example teaches sloppy output. So the examples have to be the standard you actually want, because few-shot does not just suggest a pattern, it makes the model imitate the one you gave.