This is what happens..
You meet in this conference room. Dean healy gives a talk. Then you have 2 one-on-one interviews with faculty members -- one right after the other. They give you an essay to write (It's easy. I promise.) Financial aid talk. Tour. Student interview/lunch. Student Tour.
Just be yourself and know your application well. They will definitely ask you questions about it. Read the interview feed back page to get an idea of questions they're going to ask. And most importantly, RELAX! It's not a stressful interview at all!
Congrats on the interview invite!