What is the difference between a psych nurse and an RN?

Does it involve a certification or do I have to minor in psychology or go through a master's program? What differs in their responsibilities? Where do psych nurses work?

I'd like to know the same things for a nurse practitioner.

View this post on my blog: http://travelnursesuccess.com/what-is-the-difference-between-a-psych-nurse-and-an-rn