An artifact is work Claude puts in its own panel, beside the chat, instead of burying it in the conversation. Think a document, a table, a chart, a checklist, or a small single-page app. Because it sits on its own, you can edit it in place, keep versions, download it, and reuse it later.
A normal reply is fine for a quick answer you will read and move on from. Reach for an artifact when you will edit, keep, or use the result outside the chat.