Hi friends, in this AI Masterclass episode (part 17), I explain one of the most critical beginner concepts you must understand: the system prompt. A system prompt is a hidden instruction given to the AI before you even talk to it. You don’t see it, but it controls the tone, behavior, rules, and personality of the model—whether you’re using ChatGPT, Google Gemini, or Copilot. In simple words, it’s the invisible layer that shapes every answer you get. I also share the mental model I want you to remember: a prompt is what you ask, but a system prompt is how the AI is wired to behave. Think of it like a manager giving instructions to a digital intern: “be polite, never reveal private data, answer like a senior developer, keep it crisp.” This is why system prompts matter so much for guardrails, governance, privacy, and security. When users ask for something harmful or try to extract private data, the system prompt is what steps in and blocks that behavior. If you’re building agents, this concept becomes foundational because it defines safe, ethical, and consistent AI behavior across the entire app.