Visions (as opposed to the more mundane hallucination) and schizophrenia
I want to say first that there may be no way to tell these two categories (visions vs. hallucinations) apart. But I don't mind drawing a distinction quite clearly by definition.
An hallucination is the product of a diseased or damaged brain (remember, non-organic psychological trauma is also damage to the brain), and manifests itself as sensory experience with no basis in reality. At its easiest to distinguish, the hallucination clearly takes place in space and in time, with no transcendent quality at all.
A vision, on the other hand, is real but in a transcendent ("super-real") way. The visionary does not usually confuse the content of their visions with their experiences in normal reality, even though their visions may be described in worldly terms.
Here is an example, by way of explanation. In a transcendent state, one has access to the presence of many, many other people and times all at once. The beauty inherent in the experience can combine with this simple fact to create a vision of mankind living together in harmony and love. The visionary may "return" with a sense of heaven on earth being somehow possible, sinc ethey have felt it themselves.
Some examples of hallucinations might be suffering the observation of objects or hearing of voices that are clearly not there to others in your presence, all the while being firmly rooted in the place and time occupied by your body.
A grey area here would be the concept of involuntary transcendence - the door to the other place is open but not of your will or under your control (or even at your desire) and information comes tumbling through, perhaps disorienting you but not creating a straightforward transcendent experience. You are still attached to space and time, and yet things from another dimension (if you will) are forcing them selves into your consciousness and demanding to be interpreted.
As you can see, a schizophrenic might be someone with brain damage (on a large scale, psychological/neuronal, or chemical level), they could also be someone who experiences vivid transcendent experiences (and they are nothing if not incredibly vivid) without understanding what they are, how to assimilate them, or perhaps just not realizing that expressing them carelessly will get them locked up for their own "protection."
© Huw Powell