A Manager is concern about performance, managing and leading the work of the employees under his supervision.
A Manager trains employees for the sake of company goal, business-related objective. The concern is about performance while the mentor is about the individual.
Mentors teach free of power, flexible, non-formal approach while Managers do in persuasive and commanding ways, and that the employees being trained are obliged to learn, and enrol themselves under the directions for the work.
A Mentor provides a learning option " either you follow or not."
A manager in its own term is an authority and authoritative rule " you should learn and follow."