The Sanskrit word karma basically means to do or act. In most basic terms, the law of karma states that one reaps what one sows. The law of karma implies that every thought or deed, whether they are good or bad, will count in determining how an individual will be born in their next life on earth. So an individual with bad karma could be born many different times into lower castes of humans or even into lower forms of animals. In Hinduism, the person cannot be released until they are reborn into the Brahmin or priestly caste. So this is how karma and reincarnation are intertwined. So in reality individuals are in control of their salvation, which is their release from the cycle of birth and rebirth.1
BTW, that is absolute nonsense. You can't analyze something when you start with an entirely erroneous premise about it.
And in turn Christians respectfully but emphatically disagree that the sort of thing you describe is a fundamental driver of the universe. A doctrine of karma may be an approximation to truth, but isn’t an ultimate fundamental truth which is revealed by a triune God in the Judeo-Christian bible. This disagreement has serious consequences, for one the Eastern religions’ insistence that Jesus Christ could not break “karma” by shouldering the load of sin voluntarily.