If you think a lot about leadership stuff, you may have your own way of defining the difference – something like ‘managers concentrate on doing a thing right, leaders are interested in doing the right thing.’ Here’s something from Dan Allender in his fascinating book, Leading with a Limp:
The difference between a manager and a leader is the internal urge to alter the status quo to create a different world. In that sense leaders are prophets. They see the present as incomplete and inadequate and are willing to risk the comfort of the present for the promise of a better tomorrow. A manager, on the other hand, is content to keep the organization running as smoothly and as efficiently as it can function. A manager serves to keep the plane in the air, whereas a leader wants to put a new engine on the plane midair.