The word 'Karma' is actually a Sanskrit word which literally means "action" or "deed". In English the common usage of the term 'karma' is actually a shortened form of the Sanskrit word 'karmafala' which means "The consequences of action" (Karma - action, Fala - consequences).
And thats how simple it is. It only means the 'consequences of your actions' and its both simple and brilliant at the same time.
A typical example of 'karmafala' at work is suppose a man who gets drunk and beats up on his wife(karma).
Well he soon might find himself ending up in jail or find his wife leaving him, leaving him lonely, bitter and miserable (fala).
So the concept of karma does not really try to explain the great mysteries of this universe neither does it try to dictate behavior.
It simply calls out to all of us to weigh the consequences of our action.
You cannot really compare 'karma' to organized religion. However I am an atheist and I believe in logic, science, reason and rationality wedded with human compassion and kindness and I find the concept of karma to be useful.
I do not believe in organized religion since it is based on blind faith (and hence not on reason/science) and it always ends up with a group of people dictating to another group about how to lead their lives.
It is better to die on one's feet
then live on one's knees
