Explain the following concept.
Hallucinations are false perceptions in the absence of appropriate stimuli. Hallucinations are a symptom of schizophrenia and other mental disorders. Commonly occurring hallucinations are visual, auditory, tactile, gustatory, and olfactory in nature. For e.g., the person may hear voices telling him to do something. Hallucinations are also noticed due to substance abuse, medications, epilepsy, etc.