My experience is it can mean different things at different schools. Usually it means they don't have your "vitals" - namely GPA and MCAT score, since those are the most likely to pre-bias an interviewer's opinion. At UIC closed-file meant that the interviewers had only my essays, but didn't know where I went to school, my major, MCAT score or GPA. But a lot of them asked me anyway, and I was happy to tell them (where I went to school and major that is, nobody asked me my MCAT score). Usually though, closed file doesn't know anything about your activities or accomplishments, and so it's more conversational - they want to see how you come across and how you communicate on the spot rather than what you've put down on an application. It's challening, but more interesting in my opinion - it seems more like a "getting to know you" session than a rundown of your college career.