In the most basic terms, a mentor is a teacher. However, as the definition indicates, a mentor has certain qualities that distinguish him or her from other teachers, most notably wisdom
Any teacher can relate information to a student, but a mentor achieves a special kind of rapport with his or her student(s). The mentor's way of teaching coincides with the student's way of learning, and the student therefore learns much more quickly and with greater zeal than they would have otherwise. Learning things they never would have believed they could understand gives the student confidence in their own ability to learn, and the mentor takes it one step further by displaying a great sense of character.
This sense of character turns the mentor into more than a good teacher; in the student's eyes, the mentor represents an ideal one should aspire to. The mentor's worldview, way of thinking, and sometimes even his mannerisms all seem to the student to be worthy of adoption as the student's own. It should be noted that the mentor is never an object of worship, because part of being a mentor requires that he or she seem distinctly human, rather than superhuman. Unlike a religious figure, who represents an inherently divine, superior being, a mentor shows the student how great a normal human being can be.
Most people can recall their favorite teacher or teachers from school, and such a teacher may be thought of as a mentor. Inside or outside of a school setting, few ever forget the knowledge their mentor taught them, and fewer still forget the life lessons they learned from their mentor.