A Neuropsychologist is a licensed psychologist trained in the science of brain-behavior relationships.  Neuropsychology is a specialization within the more general field of Clinical Psychology. The doctoral training and degree are typically in Clinical Psychology but the Clinical Neuropsychologist must have also completed a two-year postdoctoral residency, or equivalent, in Neuropsychology. Board certification is not required but is further evidence of competency and qualifications to practice Clinical Neuropsychology.
Neuropsychologists are different from other doctors. For example, Psychiatrists receive a medical degree (M.D.) and then specialize in Psychiatry during their residency.  Psychologists receive their training in the science of human behavior and receive a graduate degree (Ph.D. or Psy.D.). Psychologists are not medical doctors and cannot typically prescribe medications.