"RAG is based on a very intuitive idea: to avoid LLM’s hallucination, it retrieves the most relevant information from a knowledge base and uses it to ground the LLM’s answer."

Is "avoid" supposed to imply that RAG eliminates the tendency for LLMs to hallucinate? Because it definitely does not, and can not, eliminate hallucinations (or more properly, confabulations) from LLM output.

It is in an inherent aspect of these statistical inference machines that they will generate synthetic texts based on an aggregate of token probabilities form a cohort of texts. Sometimes those probabilities will generate token sequences (aka "text") that has no bearing on reality or facts.