There are lots and lots of blogs, books, magazines and people who assume that a leader and a manager are the same thing, but they are not.
Just take the name of someone famous in history, someone who used to lead people, like General Patton or Field Marshall Rommel. These men had high military ranks and undoubtedly, they were very good at what they used to do. Fighting in a war is not just to know where to drop bombs or put your tanks; as any military commander could tell you, there is a lot about knowing how to deal with people under terrible circumstances. Managing an army is a complicated thing indeed, but there are thousands of officers and NCOs to do that. You have plenty of sergeants and lieutenants but, are they all leaders? You have even quite a few generals and marshals of equal or even greater rank than Patton or Rommel yet, does that turn them into leaders?
The military metaphor is very good to explain the difference between a manager and a leader: all non-commissioned and commissioned officers mage resources, weapons and personnel. Maybe a corporal manages two soldiers and a general twenty thousand, but they essentially do the same at different levels. Yet, not all people with some rank in an army rises to become a true leader that inspires its troops and gains respect not only by his nationals, but even by his adversaries. Unfortunately, common knowledge seems to make people who read self-help, motivation or leadership blogs, magazines, etc that both things are the same, perhaps in order to enhance the self esteem of some of those who are interested in the concept of leadership.
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Very often, such individuals have some sort of managerial position within a corporation, and is natural that they want to increase their performance and gain promotions, but many times also, managerial positions are just rather lame desk jobs. Such people need not only a leadership boost but a self-esteem one and perhaps, publishers sense that and try to say something nice. So, here you have some good and bad news:
If you are a manager with a desk job it is rather unlikely that you are a leader. That's the bad one.
But the good news is that you can change and you can become a true leader, provided that you are ready to think out of the box because leaders, by definition, think differently than the average Joe.
You should begin by understanding and accepting the difference between the concept of manager and that of a leader; both are important in their own ways but while a leader might be a manager, a manager might not be a leader. Leadership is something that goes a little bit further than management. In brief, you could say that a manager "manages", takes care of what exists, lives mostly in routine, while a leader "leads" into new horizons, creates and seldom ventures into routine chores. Both of them, however, are important: You cannot manage an organization without good managers, and you cannot ensure the survival of the organization and its success without leaders capable of taking it forward.
Probably you are a good manager, but in order to be more than that you should start thinking creatively, looking for new solutions to old problems, and being always ready to go an extra mile for whatever you do.