An AI hallucination is when an AI gives details that are wrong or made up, even though the answer sounds confident. It is like a storyteller who fills a gap with an invented detail without warning you.
An AI might name a book that does not exist or give an incorrect fact. This can happen because the system is generating a likely-sounding response, not checking every sentence against reality.
Check important claims with trustworthy sources, especially before acting on them. A confident tone is not proof that the answer is true.