People tend to use the terms manager and leader interchangeably. However, they differ. Leading is one of the four management functions (planning, organizing, leading, and controlling). Thus, management gives position power and is broader in scope than leadership, but leadership is critical to management success. A manager can have this position without being a true leader. There are managers—you may know of some—who are not leaders because they do not have the trust and ability to influence others.
There are also good leaders who are not managers. An informal leader, an employee group member, is a case in point. Today, leadership is a serial emergence of both official and unofficial leaders as part of a simultaneous, ongoing, mutual influence process, as in participative leadership. Hence all leadership is shared leadership.