In other words, what to answer to "do you have any questions?"
This is the best part of an interview because it gives you a chance to show your interest as well as your intellect, creativity, wisdom, knowledge, and approach.
There are many perfect, experienced candidates that totally fail the interview because they don't ask any questions. It is a fatal error. In a lack of questions, candidate displays a lack of passion.
Asking questions is a bonus, especially if you didn't do so well during the interview. You can use this opportunity to gain back points. A few thoughtful questions that stun the interviewer can balance out your lack of experience.
Ask as many questions as you like—the interview is over when you quit asking. So if you can keep the conversation going with some great questions for few minutes, you might come out as a top candidate for the position: the passionate person who really wants to work for this particular company.
Smart managers always hire for attitude over skill.