If I had a nickel for every time someone asked me this question, I wouldn't have to pick up nearly as many overtime shifts.... (Also, if I had a nickel for every time someone asked me "You're so smart, why aren't you a doctor?" I'd have the beginnings of my endowment for a nursing theory based medical school, but that's a different/future post and rant...) There is room for a lot of nuance in this explanation that I'm not going to touch on in this post. I'm going to do my best to give a solid, simple overview.
To begin, all nurse practitioners (NPs) are registered nurses (RNs), but not all registered nurses are nurse practitioners. There is a hierarchy of training involved in both jobs. A nurse practitioner requires more eduction, either a master's degree or a doctorate of nurse practitioner (side note: the level of education required is becoming an increasingly controversial area in nursing and may also result in a future post). Registered nurses require only a minimum of a 2 year degree in nursing to sit for their licensure, but there is a large movement in nursing for all RNs to have a 4 year degree in nursing. At the end of their education, both RNs and NPs must sit for their respective standardized exams in order to obtain a state issued license that will allow the RN or NP to practice medicine.
The next big and most important difference is scope of practice i.e. what are RNs and NPs allowed to actually do. The scope of practice for each is designated by the particular state that the RN/NP is practicing in and it can vary widely from state to state. But the main difference is the level of authority each has in their medical practice. A nurse practitioner can actually prescribe medications, perform some procedures, order medical tests and give you a diagnosis, similar to a doctor, though more limited in scope. A registered nurse cannot do any of these things. The line can feel convoluted at times because RNs are good at their job. They might be able to listen to someone's lungs and know that they probably have asthma, but RNs cannot officially tell someone they have asthma, order their inhaler, or send a patient out for further testing.
So there you have it. Those are the big differences. Both NPs and RNs share the same theory base and approach to care. Each role has its pros and cons. But together, RNs and NPs help to make up the necessary team for ensuring that patients get the kind of holistic care they deserve.