D.O. Some physicians attend osteopathic medical school instead of allopathic medical school. They earn the do degree instead of the md degree. Historically, there are some differences in regards to the training philosophies and you can certainly investigate those on your own, or discuss with the physician you were referred to. You will likely encounter both degrees in various practice settings.
Doctor of Osteopathy. A do is an osteopathic physician. Do's are fully licensed physicians who can practice in all 50 states, writing prescriptions & performing surgery, in essence, the same as their allopathic colleagues (md's). Their training is such that they also learn spinal and extremity manipulative therapy for various musculoskeletal disorders.