Schizophrenia is a chronic mental illness characterized by abnormalities in perception, thought, emotion, behavior and communication. It is classified into several subtypes including paranoid, disorganized, catatonic, undifferentiated and residual. Symptoms vary depending on the subtype but may include hallucinations, delusions, disorganized speech and behavior, lack of emotional expression, and difficulties with daily functioning. Treatment involves hospitalization if needed for safety, as well as biological therapies like medication and psychosocial support.