Since karma has found itself in the mainstream English dictionary, here, I will continue to use it as an English word instead of, and alongwith, interchangeably with action.
No karma is done without a reason, purpose, intent, motive. It is not possible to generate the will to act without them. While the physical action obviously brings a physical manifestation-as the result, the reason for your body to be propelled to act, it is the intent also, which affects the outcome.
How much does the intent affect the result?
For very apple seed sown you get an apple tree, is the physical aspect of the law. A दृष्ट फल Drusta phala. An observable, seen result. Then there is the delayed result, which is subtle. And also not immediately experienced. It is called the अदृष्ट फल adrusta phala. The immediately unobservable, unseen, but will surely be seen at a proper time, some time. It is a delayed result. How many apples will the tree yield? What would be the taste? This cannot be known when the seed gets sown. This remains unseen. But get known when the tree matures and yields fruit.
Karta —> karma —> drusta phalam + some adrusta phalam.
Karta -the doer, the decider of the action, engages in the karma, action. And that action will bring back to him results in two pronged way. The immediately observable, which will be seen shortly after the completion of the action and the immediately not observable result, which will be seen much later. And so remains unrecognised, ambiguous when it fructifies. Best known only as Luck. Good / Bad are decided by the experiencer of it.
The Drusta phala gets destroyed once it is expereinced, consumed. The adrusta phala gets destroyed when it becomes Drusta phala. Take it as in the analogy of an apple seed sown. It takes time to yield the fruit. While the fruit has not matured yet, it lays latent in the tree. But, once it has, it is now ready to be consummed. That fruit gets destroyed but its seed is still there. Lives long enough. But is perishable. Before it does, it can possibly restart the cycle of seed-fruit-seed, or perish from its ‘seed-ness’ loosing its seediness.
No karma can be disconnected with the karta-the doer. And no karta can be disconnected with his motive for the karma. Thus, common sense says, the result of karma must be enjoyed by the karta and also that each one’s differing intentions must be a major reason for the differing results for each. Since it is a common observation, that even when the same physical action is done by different people, the same result is not experienced by them.
Law of causation explains only the Drusta phala -seen aspect. For every cause there is an effect. This is a linear equation which covers only the immediately seen. Where Law of karma explains both the immediately seen and the also immediately unseen, but will-become-seen-later aspect. Understanding the Law of Karma means understanding that karma has adrusta phala, which is far greater in implications than the drushta phala.