Is a group working together for one cause, leaded by one person, working as one unit. Of course this goes for bad people as well as good, like Hitler for instance. But on the good side of things, there could be a officer in any kind of force (police, army, etc.). Leadership is also fighting the good fight all you can with the team, maybe even sacrifice for the team. The world would have gone nowhere without leadership, without someone devoted enough to keep going.