Prompt

A prompt is the input text given to an LLM that conditions the response — a single sentence or a layered structure of system instructions, examples, and user questions. Modern APIs typically structure it as a System Prompt plus assistant and user messages. How the prompt is written has a direct impact on output quality, which gave rise to the discipline called Prompt Engineering. The fact that the same model can answer the same question with very different quality under different prompts is what underpins the framing of the prompt as a "new programming interface."