Schizophrenia (the real deal that is) is a medical condition in which the senses of the body don't work right. People who suffer from this see, hear, taste, feel, and smell things that aren't really there. For instance, a schizophrenic person can think everyone around them is bleeding through their skin, they can think that they're talking to someone who isn't really there, and they might think that there are voices taunting them in their heads.
Those are just examples of what could happen. I'm pretty sure each schizophrenic is different, suffering from different illusions. The thing that remains the same is that their sensory abilities have gone haywire. I believe they can take medications to calm their nerves down.