What makes a hero?

When thinking about the construct of hero, I usually don't think about anything other than main character.

But in literary terms, the hero is the character that brings about the most change. It is the Hero who gives the story the purpose. He defines a role that we want to champion the defense and directions, moan poor choices and provide a self reflection that makes us better people in real life. 

Heroes in children stories can be very simple. They have faults like Arthur of the Arthur anteater. They give us hope like Frodo of Lord of the Rings. They remind us that even hero worship has limits like in Harry Potter.

But why the exposition? Because I'm looking at the construction of hero and teaching heroes. It could be a whole theme. I will sort out the ideas later. NaNoWriMo is on the horizon.