Prompt

A model only knows what is in the prompt and what it learned in training. That is why a vague request gets a generic answer, and a request with context gets a useful one.

System prompt

Besides what you type, products usually send a system prompt: fixed instructions that apply to the whole conversation, such as tone, rules and available tools.

When a prompt becomes something else

The text you paste every week can become a skill: a file the agent loads on its own when the task calls for it.