01In plain English
A hallucination is when an AI model produces something that sounds right but is false: a statistic that does not exist, a quote nobody said, a court case or research paper that was never written.
02Why it matters when you are choosing
Hallucinations are why AI output needs checking before it is published or relied on. Tools that cite sources, or only answer from your own documents, make errors easier to catch.
03What to check
Ask the vendor
Check whether the tool shows its sources, whether you can limit it to your own material, and test it on questions you already know the answer to.