During a job interview, you are usually expected to ask pertinent questions related to the position you are seeking.
A good interviewer will ask if you have any questions. If you are not invited to do so, you should take the initiative to ask questions anyway.
Your questions are indicative of your motivation, objectives and interests. Your prior research on the organization and the career field will help you formulate good questions.
Be sure your questions are meaningful and job related. Try not to ask for information already available in the organization's brochures or other material. However, company materials and recently published articles about the organization are excellent sources of information to help you develop your questions and comments.
Remember that asking good questions is a chance for you to demonstrate your motivation and interest in the job. Plus it is an opportunity for you to get the information you may need later on when evaluating job offers.