An interview is your window to demonstrate why you are the best person for the position. It's also an opportunity for your prospective new employer to learn more about you, your experience to date, and to get a better understanding of your personality and career aspirations.
Always remember, if you have been invited to an interview they are already interested in you and feel you have the right skill set for the job - now it's down to you to show your ability.
Also remember, it's a two way process; your interview is also your opportunity to learn more about the company and the role on offer. As much as your interviewers will be gauging whether you are right for them, it is equally important that they are right for you.