i'm quoting from the book by annette t. vallano, m.s., r.n., c.s. titled your career in nursing: manage your future in the changing world of healthcare published by simon & schuster in 2003. isbn# 0-7432-3521-5, paperback, $18.00 retail. on page 48 the author says:
"nurse practitioner (n.p.)
"these nurses provide all primary care services, including administration of immunization protocols, ordering and interpreting x-rays and laboratory data, etc. they practice in a variety of specialties such as adult health, pediatrics, women's health, family health, as well as psychiatry and mental health. they can prescribe medications in all states, with 18 authorizing this practice as an independent function without requiring physician collaboration. they work in clinics and hospitals in metropolitan and rural areas, especially in places with underserved healthcare needs, and in private practice as well. professional certification is usually required by employers and insurance companies that provide reimbursement of healthcare expenses. the n.p. has more broadly defined functions when compared to the c.n.s. (see below).
"clinical nurse specialist (c.n.s.)
"this nurse has highly specialized skills and is prepared to practice in a wide variety of nursing areas including psychiatric/mental health, community health, oncology, pediatrics, etc. primary roles in which the c.n.s. functions often include acting as a patient advocate, as well as educator, clinical resource, consultant and role model to other nurses, especially those practicing at the generalist level. c.n.s.s can be found in all employment sectors of the healthcare industry as well as in private practice; the psychiatric clinical nurse specialist often has his or her own practice. like the n.p., professional certification is typically required or advantageous."
i hope this is of some help to you. by the way, i highly recommend this book. it's come in handy a lot lately for me.