This question is an opportunity for you to make your case for yourself as a candidate. You can talk about your qualities (hard worker, skilled communicator), but try to provide evidence of how you've been an asset in previous positions. For instance, you could say, "I'm a skilled communicator and passionate about helping my clients get a positive media reception. In my position at ABC agency, I was able to increase [client name's] mentions in the press 30% from one quarter to the next."