This question gives you the chance to direct the conversation towards your strengths, your interest in engineering, and your desire to work in the position for which you applied. Avoid giving the interviewer your whole life story, but do provide some background about what initially piqued your interest in engineering. Then, explain why you chose your specific major, and why you are applying for this job. In your answer, show the interviewer the impact you hope to make with your career. This could be general, such as 'improving people's daily lives', or it could be more specific, such as 'contributing to the project to put a man on Mars'. In either case, choose an impact directly related to the job for which you are applying.