PA's are physicians assistants. After completing your Bachelors degree, you can go directly into a PA program. Once a PA, you will work under the supervision of an MD. NP's are Nurse Practitioners. You must practice as a registered nurse, before becoming an NP. The biggest difference between the two is the training. Most PA's train directly with medical students, and are trained like a doctor. NP's are trained like nurses and are more patient care focused.