This document discusses various theories and concepts related to leadership. It begins by defining a leader and leadership, and distinguishing between leaders and managers. It then covers historically important early studies on leadership from Ohio State, Michigan, and Iowa. The document outlines several traditional theories of leadership including great man theory, trait theory, and contingency theory. It also summarizes modern theories like transformational, transactional, and authentic leadership. Finally, it discusses different leadership styles, substitutes for leadership, and approaches to developing effective leaders.