A veterinary specialist is someone who completes three to four years of additional training, usually in the form of an internship and residency programs, after graduating from veterinary school.
Following the advanced training, credentials must be submitted to the specific group in question, i.e. American College of Veterinary Internal Medicine (ACVIM), American College of Veterinary Surgery (ACVS), etc. After preliminary criteria have been met, the individual must pass a multi-day examination. Once the individual passes the examination they become a member or diplomate of that group and are considered to be board certified.
In general, veterinary specialists see cases requiring advanced training, expertise, skill or equipment for diagnosis and to perform the most up to date surgical or medical treatments for the pet. Canine orthopedic surgery, complicated abdominal, thoracic or cancer surgery, ultrasound, chemotherapy, endoscopy and MRI/CT scans are a few examples.