Decoder. plain-English AI glossary

User message

● Core

A turn in the conversation spoken by the person — what you actually type in.

Think of it like

Your side of the text thread: the questions and asks the other party responds to.

Example

“Can you make that shorter?” typed into a chatbot is a user message.

How it actually works

User messages carry the human’s requests within the tagged turn structure. The model reads the whole running sequence of system, user, and assistant turns to decide its next reply. Anything untrusted a user pastes in also lands here, which is why injection risk lives at this boundary.

For product teams

This is where untrusted input enters — treat its contents as potentially adversarial.

For engineers

A conversation turn with the user role; the primary untrusted input surface.

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