This is a big order for a small post. Hopefully, I can start the ball rolling with others helping out the points I miss...
Osteopathic medicine awards a D.O. degree. Allopathic medicine (traditional) awards a M.D. degree. For all practical purposes they are the same degree. Each allows to practice all types of internal medicine and (sub)specialities and including surgery.
The main difference between the two "on the books" is in philosophy. Osteopathic philosophy believes that body as a unit is self-healing and it is the role of osteopathic medicine to work within that context. Additionally, a tenet of osteopathic medicine (similiar to surgeons) is proper structure begets proper fuction. As a result, osteopaths are trained in Osteopathic Manipulative Therapy (OMM). This training, which is not learned as an MD, includes physical manipulation (usually of the spine) to promote proper structure (hence proper blood flow, nerve function, etc etc). Lastly, osteopathic medicine at its core is more holistic than allopathic medicine. This refers to working with the patient as a whole person including physical, psychological, and enviromental factors when treating an illness.
My reference to "on the books" means that this is the inherit philosophy of osteopathic medicine. In reality, many (most?) DO's practice just like MDs (and vice versa).
Hope I helped!
-A
