I had one on-campus interview with a recruiter, who asked me questions concerning what aspect of computer science I wanted to work with. The second interview lasted half a day. I had three 30 minute 1:1 interviews and in between said interviews, I mingled with other applicants, who also had one on-campus interview. After the last interview, I was taken out to lunch with a current employee and two other applicants.
During the day interview, I had the opportunity to meet a lot of current employees. They all seemed very friendly and had volunteered to mingle with us, so they clearly enjoyed their jobs and were interested in meeting the future employees. All of the interviews were more like regular conversations you might have with someone who wanted to get to know you. They asked about previous projects I had been involved in, but it felt like a conversation for the most part.