Prompt engineering is the work of writing the instructions that lead a model to a usable result. It covers the task, the audience, the format, the limits, and a few examples of a good answer. Same model, different instructions, different output.
It is the cheapest place to start and the first place people stop too early, or cling on too long. Spend a day on the instruction before you fund a bigger build. Then stop when the failures are about missing documents or a habit the instruction cannot hold. Clever wording will not give the model a fact it was never shown.
Think of it this way: Prompt engineering is the instruction manual you write for a very capable but very literal new hire. Vague instructions produce vague work. Precise, structured instructions produce consistent, useful output.
A sales team improves their AI email generator by adding company tone guidelines, a required output format, and three strong examples to the prompt. Quality improves without touching the model or the infrastructure.
A finance team asks a model to flag odd expenses. The first instruction, check this sheet, returns vague notes. The next one says: list lines over the policy limit, quote the rule, and ignore lines a manager already approved. The second version is the same model and a different job description.
Before trying anything more expensive. Clearer instructions often fix most quality problems, and you can change them the same day the requirement changes. When the failure is not the wording. If the model does not know your facts, a better sentence will not make it accurate. It needs your documents in front of it, or extra training on your own examples.
RaftLabs points the model at your documents and your rules, then checks the answers against cases you already trust. That surrounding work is where these projects succeed or stall. The related work on our side is Prompt engineering.
This sits with the other building & tuning terms on the glossary. How a general model gets pointed at your documents, your tone, and your workflow. Worth reading next: Fine-tuning, Retrieval-Augmented Generation (RAG), and Embeddings.