A big shout out to my brother for finding this image on imgur.
There is a significant difference between a boss, manager, and a leader. Being one does not imply being the other. These statuses can be distinct as much as they can be mutually inclusive.
There is a great deal of theory and research on the subject, but I find the image above sums it up quite nicely.
I will simplify some of the concepts below in order to make a concise point, so all you behavioural scientists, organizational analysts, and motivational speakers out there please cut me some slack when I say:
A boss is someone vested with positional power to make others do work.
A manager is someone who is good at juggling the resources needed to get a job done.
A leader is someone who can influence others in such a way as to accomplish a greater goal.
In an optimal organization, the boss is a an efficient and caring leader and a skilled manager. The boss need not place his desk apart from the others, nor whip them to achieve performance. She/he must share hardship and set the example. She/he must never ask those who work for her/him to do something she/he would never be willing to do herself/himself.
When a leader-boss-manager balances this triad appropriately, great things will happen.