Karma is among the most used, yet misused and misunderstood concepts today. Yes, it is said that as you sow so shall you reap. More simply it means what goes around comes around. Put more explicitly it can be said that your deeds, good or bad, will be repaid to you in kind.
All this boils down to the principle of cause and effect, which is what Karma basically is. This is quite a scientific, yet commonsense concept. For isn’t it commonsense that tells you that if you plant weeds in your garden, it won’t yield flowers. You don’t even need to know the law or concept of Karma to understand this.