Each student at Cambridge has a Director of Studies whose task it is to keep a student's academic progress under review, advise on choice of courses and recommend specific programmes of study.
A College officer responsible for the overall conduct of a student's academic work, including advice on examinations and lectures, and for the assignment of the student to one or more Supervisors. The term Tutor is not used in Cambridge in this connection.
The person who organises your academic life. Your DOS will usually be a fellow of Corpus, but for a few minor subjects you might have a DOS based in another College. His or her main duties are to talk to you about your work at the beginning and end of term (and at any other time as might be necessary), arrange supervisions for you, and generally tell you about anything you need to know related to your course - such as information about exams. Depending on your subject, your DOS may or may not also supervise you.