It really depends on the school. I had a few different types of interviews:
- Open file, where the interviewer has a copy of your entire application and will be able to ask you questions about anything. Pro: you don't have to remember to talk about all of your activities. Con: you may have to discuss grades that you wouldn't have talked about at all if the file was closed.
- Partial open file, where the interviewer gets a copy of part of your application. Sometimes it's just your personal statement, other times it's everything except for grades and MCAT score. The personal statement ones were a good balance because the interviewer had a starting point but not ALL of your info, so he or she wouldn't be swayed by numbers.
- Closed file, where the interviewer gets no information other than your name. It's good because you can really spin everything your way, but can also be scary because you don't want to forget anything important.
- Panel. I only had one, and it was open file with two faculty and a med student. At this one, they just asked each individual certain questions (they didn't just throw out questions to see who would answer first/best). Not my favorite, but not as bad as it was rumored to be.
Schools will mix this up. Sometimes you'll have two interviewers, both open, both closed, one with a PS and one closed, etc. Sometimes it's just one interviewer for an extended time. Sometimes you get a faculty member and a med student, two faculty, a faculty member and an adjunct faculty member, or a single interview and a panel interview. At one school I actually had to take a copy of my application with me to the room (the school gave us the copy in our interview day folder). Just be prepared to discuss anything on your application. And be yourself. Just talk to the person and answer the questions, be friendly, candid and honest, and you'll be fine.