Your interview is your opportunity to demonstrate to a potential employer why you are the best person for the position. It also gives your prospective new employer an opportunity to learn more about you and your experience and to gain an understanding of your personality and career aspirations.
Remember, if you have been invited to an interview they are already interested in you - now it's down to you to show your ability and confidence to do the job. This will also be your chance to learn more about the company and the position on offer. The interview is very much a two-way process. As much as your interviewers will be gauging whether you are right for them, it is equally important that they are right for you.