The Committee also ensures that the student is taking appropriate courses, is receiving training to carry out the research, is familiar with the research literature and is preparing for the oral defense.
My best advice would be to stay relaxed and just "have a conversation" with your committee. My husband was so nervous that he got tripped up at a simple question, and I know that was not the professor's intent. The professor went on to draw my husband into a conversation about the question, and my husband started to relax and got back on track. Just remember, your committee wants to see you succeed. Also, does your school have any doctoral programs? If they do, find a doctoral student--from any area--and see how their oral defense went. Since the committee members are chosen from different areas of the University, the format should be fairly similar even if they are in a different department. And...at my husband's defense, he was expected to bring snacks--we took some assorted cheeses and crackers. Good luck!!
What happens at a Master's thesis oral defense
The Ph.D. dissertation is the document summarizing the original scientific research in recognition of which the Ph.D. candidate seeks the doctoral degree. The University has very specific rules about the format of the thesis, but the nature of its scientific content is at the discretion of the student, his or her advisor(s), and the Ph.D. thesis defense committee. In many cases, the thesis consists of a linked set of published or soon-to-be-published scientific papers.
When informed by the student's advisor that the thesis is ready to be defended, the graduate committee selects a Ph.D. thesis defense committee. The defense committee consists of five or six members, a majority of whom must be members of the department. One defense committee member, other than the thesis advisor, is appointed as committee chairperson by the graduate committee. Within two weeks of receiving the thesis, the defense committee chairperson polls the committee members to ascertain that the thesis is actually defensible. If it is, the defense committee chairperson formally schedules the oral defense.