Prompt engineering means shaping the model input so the model is more likely to produce the result you want. It can include instructions, examples, formatting rules, source material, and success criteria.
In practice
In practical products, prompt engineering is less about clever phrases and more about clear task design. Good prompts explain the goal, define the audience, state constraints, and tell the model what to do when information is missing.
What to watch
A prompt cannot fix every problem. If the model lacks the right data, tools, evaluation, or permissions, a better prompt may only hide the weakness for a while.