The interviewer wants to learn about your career progression. Additional responsibilities, promotions, and changes in your job title all indicate that you were competent and successful in your role. This question gives you an opportunity to go into more detail about how your job has evolved. If nothing has changed much over the past couple of years in your position, focus on what you have learned. Talk about how the changes in your job have taught you new skills and helped you develop the ones you already have. If this is your first professional job out of college, describe a past internship and things you learned, and how you evolved and worked towards developing your skillset.