An interviewer will ask you this type of question to better understand your perception of this role and how you perform the job. Most applicants will rattle off what they've done in the past or what they think the job involves. A better approach to answering this question would be to carefully review the job posting to familiarize you with the requirements and the functions it describes. You can even bring this document to the interview with you with these key elements highlighted. You may also want to contact current or former employees who perform the same job to learn more about what they did and gain some insight into the company, the job, and possibly even the person you are interviewing with.