Usually you will initially meet with your sponsor. Depending on the company, you may have a published agenda for the day. This may include simply names and times of scheduled interviews, or additional information, such as titles and departments for each person, and the purpose of each interview.
This isn't the thirty-minute on-campus interview with one person. You will spend the better part of a day meeting with several people who will determine your fate.
The interviews can range from peer level to potential managers to executives. Many companies will have you meet with several different managers, any one of whom could be your potential manager. At the peer level, you may be given the opportunity to meet with one or two recent graduates who have just begun work with the company in the past year or two. The purpose of this interview is to give you a feel for what the company and the position are really about. But do not let down your guard in this interview or get too chummy. Even peer interviews have input into the final decision. Interviews with managers two or three levels above your entry position are sometimes designed to give the executive the final rubber stamp, but are often included as a final sell for a prize candidate.
You may also be asked during the course of the day to take a test or assessment. These tests and assessments are used to bring a level of objective standardization into the hiring process.