Language works when we think the same, connecting the words to the same meanings and such. But that never actually happens 100%. It might be closer to 80%. (or if it’s a strange subject, 15%)
So this “conversation” that we’re having here is, to some degree, not actually happening.
But we pretend that it is.
So how much are we pretending? How much of the conversation is hallucinatory conversation?
Your question is related to a very difficult interdisciplinary research problem: “how does ‘meaning’ occur in human conversations?” You can approach it from e.g. philosophical, psychological, linguistic, or sociological disciplines, and fields as diverse as literary critical theory, neuroscience, and artificial intelligence also have a lot to say about it.
So to answer your question: nobody knows for sure, but if you’re interested in academic pursuits you’re headed in a great direction.