In order to understand the nature of karma more fully, we need to study and understand the nature of samsara. 

Samsara is a complex situation based on passion, aggression, and ignorance. Its essence is turmoil. But if you relate to passion, aggression, and ignorance as the path–understanding them, working with them, and treading on them–you will discover the goal, which is seeing the truth of existence as it is. 

In Tibetan iconography the activity of samsara is depicted as a wheel of life, or bhavachakra. The wheel of life represents the compulsive nowness in which the universe recurs, as the death of one experience gives birth to the next within the realm of time.

The outer ring of the wheel presents the evolutionary stages of suffering in terms of the twelve nidanas. The nidanas represent how chance occurrences can evolve to a crescendo of ignorance and death. The ring of nidanas may be seen in terms of causality, or as accidents that lead from one situation to the next.

By discovering the truth of samsara, you are discovering nirvana, or freedom from suffering.