The key differences between management and leadership are summarized below:
Management is about directing a person from one point to another using a set of guidelines and expected behaviors, whereas leadership is about guiding a person from one point to another through discussion and debate. Note the keywords directing and guiding.
Management is about directing, monitoring, controlling, and administrating. Leadership is about coaching, motivating, inspiring, guiding, and influencing.
Managers focus on short term goals, whereas leaders focus on long term vision.
Managers rely on positional powers whereas leaders rely on personal powers. Refer to The Powers of the Project Manager for more details.
A good manager may not be a good leader and vice versa.
Table 3-1 of the PMBOK Guide, 6th Edition provides a good comparison of leadership and management traits.