Definition
A prompt is the input given to a generative model: natural language, examples or constraints that state what task to perform and in what form to answer.
How it works
The model generates its output based on the prompt together with the surrounding context; role framing, task description, few-shot examples and format requirements all measurably shape the result. The practice of writing effective prompts is called prompt engineering.
Usage
Every interaction with a generative model starts from a prompt — Q&A, writing, translation, code generation, image generation. Applications also assemble prompt templates in code to call models at scale.
Related and confusable terms
A system prompt differs from a regular prompt: it is set by the developer to define the model’s overall behavior, while the user prompt is the per-request input. Both end up in the model’s context.