Are you specialized in a particular area, i.e. neo-natal, pediatric, geriatric, or women's health?
The interviewer is asking this question to hear more about your background and passion. If you are applying for a position that you don't have much experience in, don't think that you will talk yourself out of a job. Explain to the interviewer what your background is, its similarities to the position you are applying to and how your rotations or background support the position. If you have a broad background of knowledge, share what area interests you most.
"The majority of my clinicals were spent in family health. I enjoyed the opportunity to work with children as well as adults. I feel my time there made me a more rounded clinical nurse."