A prompt is the text (and sometimes structured input) you send to a model to specify the task, context, and constraints. It is useful because small changes in wording often change usefulness, tone, and whether sources are followed.
Whilst a clever prompt can look like a full product, in practice prompts alone do not create trusted enterprise answers. For example, “act as a lawyer” still hallucinates clauses that were never in your contracts. We often recommend clear prompts plus retrieval or tools when accuracy matters — and saving winning prompts into a prompt set for measurement.