What is leadership?

John Maxwell always says "If you think you're leading, yet no one is following you, then you're only taking a walk." He also says that leadership is influence.

So at its core, leadership is using your influence over someone to get them to follow you.

I would like to define leadership, and come up with a simple way to grasp the whole concept of leadership. Any helpers?

Additions to what leaderhsip is:

Leaders delay their emotions.
Leaders give credit for accomplishments to the team and take blame for failures personally.
Leaders are aware of their own stregths and weakness and work on them.
Leaders communicate with their followers.