[ncmncm]

When it's a vision, it depends what you get to see. Often enough, what you see is not literally different, but its perceived meaning is different. Sometimes revelatorily different.

"Hallucination" is a judgmental term; it may be appropriate when it is involuntary, or what you see is harmful. People with schizophrenia have hallucinations, and (in all cases I have known personally) suffer for it. Thus, "hallucinogen" is a judgmental term about a chemical, where people taking one for the beneficial effects call it an entheogen.