Human: I'm a little confused about the difference between a doctor and a physician. Assistant: 
A doctor is a medical professional who has completed medical school, followed by at least three years of postgraduate training in a specialty field such as internal medicine or pediatrics. Physicians are doctors with additional certifications and/or degrees that allow them to practice medicine independently. Doctors can specialize in any field they choose, including surgery, internal medicine, pediatrics, radiology, dermatology, anesthesiology, etc.