Why a second interview?
Because the interviewer is interested in you. Congratulations!
It is a structured interview.
Questions are designed to bring out what is not on your resume, what you have done before, with whom you’ve done it, and your character.
Questions are based on important qualities designed as competency requirements that you MUST satisfy in order to PASS the interview.
When you are preparing for the second interview, expect a lot of questions about your competencies. For example, your communication skills, your critical thinking, and your leadership skills, are some of your competencies.