Just as you want to understand the role and what you'll be doing, the employer is equally interested in getting to know you.
This kind of question is like small talk; how you answer helps the employer determine what to ask you next.
Therefore, it's best to answer this question in a succinct, straight-to-the-point, professional but personal manner.
The employer wants to know about you, mainly on a professional level but also personally.
The employer does not want to know everything there is to know about your personal life and everything you have done up until now. That's why they have your resume in their hand.
They want to know about your passions with work, career goals, experience in a nutshell and even what your favourite hobby is, as well as anything else about you aside from work that helps them get to know the real you.
How you answer this open-ended question will inform the employer how you would speak in meetings with co-workers, bosses and clients. Therefore, be prepared for this question and show the interviewers you prepared for it.
The confidence that will come across from your answer will start you on the right foot.