Identity : This is the pivot of the prompt. However you address this prompt, you are being asked about your identity. You are asked to address the fundamental nature of how you see yourself as a person. Who are you? What are you? What makes you, well, you? Admissions officers want to be able to say, “hey, I understand who this kid is and where he came from, because the kid understands this about himself and is able to communicate it in a clear, compelling fashion.” So, this essay must address your identity, however you define it.
Good questions. Supplementals are aimed at making sure you really like their school and are familiar with it. Start with the big things that you like about the school, rather than things like “I live just a mile away.” What is the FEEL of the school? What do they value? What makes them your favorite? Prove to them that you are itching to go there. In order to do this, you will need to do your research on what is different about that school. They don’t expect you to know everything about it, but you darn well better know some things that separate them from other schools.
Avoid slipping into clichés or generalities. Take this opportunity to really examine an experience that taught you something you didn't previously know about yourself, got you out of your comfort zone, or forced you to grow. Sometimes it's better to write about something that was hard for you because you learned something than it is to write about something that was easy for you because you think it sounds admirable. As with all essay questions, the most important thing is to tell a great story: how you discovered this activity, what drew you to it, and what it's shown you about yourself.