Actually, karma cannot be truly understood apart from the soul. It is for the sake of the soul's growth that karma exists. You know, I am sure, what the word karma means. It is a Sanskrit word, derived from the root kri, "to do". Whatever we do, say or think is karma. The universe is governed by a law which we call the Law of Karma. You have read much about the Law of Karma, so I need not explain it here, except to say that all one's deeds and thoughts leave their impression upon one's causal body and bring about certain results.
At the same time, the soul is far beyond the snare of cause and effect. It is the hyphen between all that precedes and all that succeeds. It is enriched by all the experiences which the personality derives through the laws of karma.