I think it is always best to explore phenomena from primary sources. Such in Buddhism is “Lamrim”, a canonic text, detailing the stages of the enlightenment, the causes, and consequences of the action. In Buddhist canonic text “Lamrim” is an explanation of 3 levels in the Path of Enlightenment, depending on the maturity of a person.
What is karma and the Law of karma?
Karma translated from Sanskrit means action. Karma is related to actions and their consequences. It is a natural rebound as a consequence of taken action. Well, for example, if you break a window in your room (especially in winter), it will be cold. It’s obvious.
Types of karma
We all know about positive and negative karma. But each of them has 3 consequences:
mature fruits (rebirth in the corresponding world),
consequences that reflect the causes (specific life events),
and the prevailing consequences (life circumstances).
There are 2 types of karma:
throwing (pushing) karma
accomplishing (forming) karma.
The main is thethrowing karma: it throws sentient being to rebirth into one of 6 worlds: reality of gods, humans, animals, hungry spirits or to hell. This throwing karma depends from the main actions in life.
However, in each world there may be better or worse circumstances (“termination”) associated with the accomplishing karma. It depends from the secondary qualities. Well, let’s say, human was ignorant, living basically only by instincts (get food and sex) – this throws him back to the animal world. However, let’s say, as the human being he had good qualities too: for example, he loved his mother very much. Then he, born as an animal, can get a good owner. Or visa versa, he can be born, for example, in the human world (good throwing karma) but may have a short life, be sick, poor (bad accomplishing karma) if before had hurt some living beings.
Some would say, that they better would be born as an animal than as a sick, poor person, but it’s not true – in an evolutionary sense the animals are in a lower world without free will and they can’t achieve awareness (and from the human state one can achieve enlightenment, become buddha). So human state is very valuable and should not be wasted.