Karma
Karma means action, work, or deed. The term also refers to the spiritual principle of cause and effect, often descriptively called the principle of karma, wherein intent and actions of an individual (cause) influence the future of that individual (effect): good intent and good deeds contribute to good karma and happier rebirths, while bad intent and bad deeds contribute to bad karma and bad rebirths.
However, my own interpretation of karma, is that Karma is like gravity. It does not mean that if you do good, you will get good. It means that, if something good or bad happens to you, and you become it, and then pass it along, then it will return to you. Take for example a day at work where a co-worker spends their day complaining. If you are unable to stop this constant flow of negative energy, chances are that you willpower will drain, and you will return home and start complaining to your family. If, however, you are able to cope with it, and even go as far as finding ways to calm your coworker, thus, resisting becoming his pain, you would then have put an end to the current karma. Once you end, there will, for the time being, no longer be any rebirth of this negative energy. That is, until new triggers in life give rise to new kinds of energies.