Karma; the term can be traced back to the early Upanishads, Hindu scholars in 1500BC, who were fundamentally philosophers (who meditate as well). The word literally means 'action, effect, fate', in Sanskrit. Although the concept of karma could be explained in great detail, I would say it is commonly perceived as: "DO good, and good will come your way, DO evil and evil will befall you".
Idealy, if everyone were to embrace the notion of karma, the world would indeed be a better place, world peace would be prevalent, and humanity would live happily ever after... but that doesn't seem to be the case, we are no doubt far from ever achieving that state. Probably because karma doesn't take effect instantly - like a robber who just stole a gold chain from a house falls into a ditch and cracks his skull, spilling his brain matter on the concrete, or a teenager telling a lie get eaten up by a swarm of locusts the instant the false truth is conceived.
But being a 'teaching' of Buddhism/Hinduism, how could those of other faiths accept this idea if thier religion differs in idealogy and belief? A buddhist friend of mine once told me that all buddhists go to hell anyway, and there are 9(or did they change it again?) layers of hell, so your actions on earth would ultimately decide the fate of your afterlife. Maybe the effectiveness of the concept of karma depends on the teaching of one's religion? It maybe might not mean much if karma only affects the fate of the carnal life alone (should there be religions that do not have afterlife). I mean, if i died, would i still persist somewhere? heaven or hell? well, it could be a state of mind - but that would still mean persistance in some form; or do i just cease to exist - dissapear into oblivion? I certainly would have more drive to be a good person if it's gonna affect my future state.
But then again, would it still be considered karma if i was only doing it to save myself?