AP Style, known more formally as the Associated Press Stylebook is a 330-page style book that addresses writing styles or 'rules' for copy written by journalists, PR firms, or news entities. It touches on adequately citing sources and correct usage of titles.
Chicago Style, also known as the Chicago Manual of Style is a much longer 950-page style book that acts as a much more robust guide for editors, authors, and book publishers.
Discuss with the interviewer which stylebook you prefer, and why. It's essential that you are familiar with both style books, but it is common for writers to lean towards one over the other.