Prompt engineering is the practice of crafting inputs to an LLM to reliably produce the desired output. It ranges from simple instruction phrasing to complex techniques like chain-of-thought prompting, few-shot examples, role-setting, and multi-step system prompt design.
Good prompt engineering can dramatically change output quality without changing the model. In production AI systems, the system prompt is often the primary "code" that defines product behavior — making prompt engineering a core engineering discipline. Systematic prompt testing and version control are as important as any other part of the AI development workflow.