Courage is somehow related to the odds of success or failure, though only in situations where failure has exceedingly negative consequences.
Courage always seems to be associated with ideology of some type, and to the "underdog" narrative. In this way it is a very personal and (in the Randian sense) selfish. In this same vein it is related to honor, which is almost entirely a social construct, meaning that in various instances the "personal ideology" could be replaced with "ideas of honor", and would make the courage much more altruistic, again in the Randian sense.
To me, it is an abstract concept, yet not overly complicated. Courage is standing up for what you know is right in the face of powerful opposition, when you stand to lose much from your stance.