What is Courage?

It is a good question. Courage must be doing something difficult, but what is difficult? Courage seems to be doing the uncomfortable, so more of a mental and emotional state rather than a physical state. In other words we typically don't call football players courageous. 

I am leaving this question open today. I don't have the answer. I have a few ideas, apologizing, doing something that may result in death, doing something not normal that is uncomfortable and the right thing. Is courage a facade? Is one person's courageous act another person's weakness? What is not courageous?