The article addresses conceptual aspects of "mentoring" as an activity and the mentor's role in professionalizing staff throughout teaching career. The conceptual and typological analysis of the mentor's activity and its role in an educational institution is carried out in legal and psycho-pedagogical terms, considering also the new challenges for teachers and educational institutions. The mentor interact with the beginners teaching staff, for the benefit of the latter, in order to generate self-confidence and own strength, in order to motivate and facilitate the professional development, for achieving professional independence, autonomy and responsibility, throughout the teaching career. The mentoring activity is examined as a methodology for the induction of debutant teachers, by teacher experts, in order to professionalize the teaching career.