In Hinduism and Buddhism, that is where the principle came from. People these days assosciate it with coincidences, and 'getting what they deserve'. In Hinduism, one achieves good karma from good deeds and living the way, which is said to accumulate. Once the lifeform dies, it advances to the next stage of life until it reaches human. A crude way to say it would be, levelling up, and then once a soul has reincarnated into a human, the idea is to reach enlightenment to move on to the afterlife.
Most people loosely assosciate Karma as something that everyone believes in. It only has religious significance to the two religions mentioned above, and Sikhism, religions formed mainly in the Indo-Pacific region.
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It's Summer, and all I can think about is Snow, so cut me some slack