The Pali word kamma or the Sanskrit word karma literally means ‘action’, ‘doing’, but in the Buddhist theory of karma it has a specific meaning: it means only ‘volitional action’ not all action. Nor does it mean the result of karma as many people wrongly and freely use it. In Buddhist terminology karma in no way means its effect; its effect is known as the ‘fruit’ or the ‘result’ of karma.
Volition may comparatively be good or bad, just as desire may comparatively be good or bad. So karma may be good or bad where good karma produces good effects and bad karma bad effects. ‘Thirst’, volition, karma, whether good or bad, has one power as its effect: force to continue- to continue in a good or bad direction. Whether good or bad it is comparative, and is within the cycle of continuity (samsara). An Arahant, though he acts, does not accumulate karma, because he is free from the fake idea of self, free from the ‘thirst’ for continuity and becoming, free from all other defilements and impurities so they don’t have rebirth.
The theory of karma should not be mystified with so-called ‘moral justice’ or ‘reward and punishment’. The idea of moral justice, or reward and punishment, arises out of the origin of a supreme being, a God, who sits in judgment, who is a law-giver and who decides what is right and wrong. The term ‘justice’ is uncertain and dangerous, and in its name more harm than good is done to humanity.
The theory of karma is the theory of cause and effect, of action and reaction; it is a accepted law, which has nothing to do with the idea of justice or reward and punishment. Every volitional action inturn produces its effects or results. If a good action produces good effects, it is not justice, or reward, meted out by anybody or any power sitting in judgment of your action, but this is in virtue of its own nature, its own law.
This is easy to understand but, what is difficult is that, according to karma theory, the effects of a volitional action may continue to manifest themselves even in a life after death.