As they read and speak with other students, most graduate students notice the use of two terms to describe faculty who are particularly influential to a student's progress: advisor and mentor. Many students use these terms interchangeably. In practice, advisors and mentors are quite different.
An advisor is often assigned to you by the graduate program. Your advisor helps you select courses and might directs your thesis or dissertation. Your advisor may or may not become your mentor.
A mentor does not simply provide advice on curriculum issues, or what courses to take. A mentor is much more than an advisor. A mentor facilitates your growth and development - he or she becomes a trusted ally and guides you through the graduate and postdoctoral years. In science, mentoring often takes the form of an apprenticeship relationship. The mentor aids the student in scientific instruction, but perhaps more importantly, socializes the student to the norms of the scientific community. The same is true in the humanities; however, the guidance is not as observable as teaching a laboratory technique. Instead, it is largely intangible, such as modeling patterns of thought. Make no mistake, science mentors also model thinking and problem solving.
Relationships with mentors tend to be deeper and more personal. Many students maintain contact with their mentors after graduate school and mentors often are a source of information and support as new graduates enter the world of work.