karma : the force generated by a person's actions held in Hinduism and Buddhism to perpetuate transmigration and in its ethical consequences to determine the nature of the person's next existence
Etymology: Sanskrit karma fate, work
Like most typical Americans, I tend to think of karma more as a "you get what you put out there" idea, or simply "what goes around comes around". From the idea that your actions have a result directly related to it, karma reminds us that we can control what we do, and what result it has on others. Without getting into a theological discussion of past lives and such eternal repercussions, I believe that whatever karma you put out there comes back and smacks you right.dab.in.the.face. Maybe its just me, but this has happened so many times in my life, I can't ignore it. When I have really wronged someone, even in crazy specific ways, the same dang thing has happened to me from someone else. Conversely, when I have done something selfless and kind, someone has been there for me in the same way some other time, for which I am always very grateful.
I guess what I am getting at is that we all need to think about how much we accept responsibility for our own lives. How we treat others and what kind of energy we put out into the world affects everyone, including ourselves. Whether you are kind in fear that your next life will be as a rat, or you are kind simply to be, think about the karmic footprint you leave. Try to be more conscious of how you treat others and the rewards will be great.
For more in-depth information about karma as it relates to Hinduism (for I am certainly no expert on the Hinduism perspective, just open to learning!):