What is a prompt? Plain-English definition for AI users
2026-11-10
Definition
A prompt is the text you give an AI tool to tell it what you want, whether that is a question, an instruction, a document to work from or all three together.
Why wording matters
A large language model can only work from what you give it. A vague prompt gets a vague answer. A prompt that states the task, the audience, the format and any facts to use gets a result you can actually send. The prompt, and any documents you attach, must fit inside the model's context window. Writing prompts well on purpose is called prompt engineering.
Vendors such as Anthropic publish their own prompting advice. A good everyday prompt covers four things: who the AI should act as, what the task is, what material to use and what the output should look like. For a worked set of habits, see writing better prompts for work.
A hypothetical example
A weak prompt reads: "Write a follow-up email." A stronger one reads: "You are the office manager at a Newcastle electrical firm. Write a friendly three-sentence follow-up to a customer who received a quote last week. Mention the quote is valid for 30 days and ask if they have questions."
The second needs a few more seconds and saves several rounds of editing. Getting a whole team to prompt well is the heart of AI adoption.