Connecting a model's responses to factual, verifiable sources rather than letting it rely solely on its training data. Grounding techniques include RAG, web search integration, and citation requirements. A grounded response says "according to [source]" rather than just asserting facts.
Why it matters
Grounding is the primary defense against hallucination. An ungrounded model confidently invents facts. A grounded one points you to real sources you can verify.