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 loosely refer to it as the ‘fruit’ or the ‘result’ of karma.
O Bhikkhus, it is volition that I call karma. Having willed, one acts through body, speech, and mind. ~The Buddha
Volition is mental construction, mental activity. Its function is to direct the mind in the sphere of good, bad, or neutral activities…Sensations and perceptions are not volitional actions. They do not produce karmic effects. It is only volitional actions—such as attention, will, determination, confidence, concentration, wisdom, energy, desire, repugnance or hate, ignorance, conceit, idea of self, etc.—that can produce karmic effects.
Volition may relatively be good or bad, just as desire may relatively be good or bad. So karma may be good or bad relatively. Good karma produces good effects, and bad karma produces bad effects. ‘Thirst’, volition, karma whether good or bad, has one force as its effect: force to continue—to continue in a good or bad direction. Whether good or bad it is relative, and is within the cycle of continuity.
The theory of karma should not be confused with so called ‘moral justice’ or ‘reward and punishment’. The theory of karma is the theory of cause and effect, of action and reaction; it is natural law, which has nothing to do with the idea of justice or reward and punishment. Every volitional action produces its effects or result. If a good action produces good effects and a bad action bad effects, it is not justice or reward, or punishment meted out . . . but this is in virtue of its own nature, its own law. According to karma theory, the effects of a volitional action may continue to manifest themselves even in a life after death.
Happiness lies not in the ability
to satisfy our every desire,
but rather in the ability
to refrain from reacting compulsively
to every craving and prodding of the mind.~ Peter Ontl
Walpola Rahula, What the Buddha Taught