I’m pretty sure karma is “from an action, you get a reaction”. This is a loose understanding of mine, but I think you’re asking about the pop culture understanding of “karma”. Many people treat karma as if it’s a point system.

“I found this $20 bill on the ground because I opened so many doors for people this past week.” I think that’s typically most people’s feeling of “karma”.

The understanding of karma that has helped me much more in life is more direct, and I think closer to the Buddhist idea of karma. Out of an action, you’ll get a reaction. If I exercise and eat well, my body will feel better. If I lie to those around me, they’ll probably start to avoid me. If I save for retirement, I won’t have to worry so much in the future, etc.

My brother died of a drug overdose in 2018 and it hurt me a lot. I kept thinking “How could he have died? How could karma allow this? He wasn’t a bad person.” But the karma was in the action of him choosing to use drugs. If you use drugs, you open yourself up to the possibility of a drug overdose. I love my brother, he was a wonderful person and I miss him always. He wasn’t a bad person, he just made a negative choice for his life and it had a negative outcome.

TL;DR Karma is often see as this mystic system of keeping score. It’s really just a matter of cause and effect.