This question is an opportunity for you to be genuine about yourself. Most people are not incredibly “unique” in the broad sense of the word. Only a few people can be Olympians or be a certain ethnicity. You can talk about your personality, experiences/background, passions, etc. Read “Weekly Weigh-in: The Diversity Secondary Essay” (https://www.prospectivedoctor.com/weekly-weigh-in-the-diversity-secondary-essay/) to learn more.