A retrieved document is information selected from a knowledge base and supplied to a model as context. In a RAG flow, the retriever searches for information relevant to the user’s query, then the generator receives both and produces a response incorporating the retrieved context. section 3.2.3
Grounding responses in retrieved evidence can mitigate hallucinations by giving the model information beyond its parametric memory. Relevant background can also frame a chatbot’s domain, such as electronics e-commerce. section 3.3 section 2.6.2

