In more detail
A system prompt is the hidden instruction sheet a chatbot receives before you type your first word — its job description, personality and rules, written by whoever deployed it. You never see it, but every single reply is shaped by it.
It matters because it explains behavior that otherwise seems baked in. Why one assistant is formal and another playful, why a support bot won’t discuss competitors — usually the system prompt. It’s also a favorite target: jailbreaks and prompt injection are both attempts to override it.
Goes with