Panel interviews will usually be more formal than a single interviewer format; the panel will generally take turns asking structured questions and will take good notes.
A panel interview consists, as you might imagine, of a group of interviewers instead of a single person. The panel interview is a time-saving method for companies who wish to have several representatives from different parts of the company see a candidate. Instead of scheduling several interviews over a period of days or weeks, the company reps can all see the candidate at once. They also have the advantage of seeing the candidate at the same time and hearing the question responses in the same context.