Hallucinations are experiences where a person perceives something that isn't present in reality. This can involve seeing, hearing, smelling, tasting, or feeling things that others do not. They can occur in various conditions, including mental health disorders, sleep deprivation, or substance use. These experiences can be vivid and convincing, leading individuals to believe that what they perceive is real. While hallucinations are often associated with conditions like schizophrenia or bipolar disorder, they can also happen during fever or severe stress. Understanding hallucinations is important for proper diagnosis and treatment.