it is the diagnostic and statistical manual, 4th revision, as stated by others. But nobody else said, it's a good question. The DSM-IV is used to "diagnose" people with mental health problems: so that, hopefully s/he can get the right treatment and also so that they can submit a code for insurance billing and reimbursement. Psychiatrists and therapists and social workers and courts use these codes to communicate info about their clients or patients. If you go on the website for American Psychological Association, you can find more information. Take care/