The bhavacakra is popularly referred to as the wheel of life. This term is also translated as wheel of cyclic existence or wheel of becoming. The bhava-cakra is a symbolic representation of samsara (or cyclic existence) found on the outside walls of Tibetan Buddhist temples and monasteries in the Indo-Tibet region. In the Mahayana Buddhist tradition, it is believed that the drawing was designed by the Buddha himself in order to help ordinary people understand the Buddhist teachings.
Already well-established in India before the time of the Buddha was the psychological system known as The Wheel of Samsara, or The Cycle of Existence, or The Path of Transmigration. It is depicted as a circle divided like a pie into six realms, each having numerous subdivisions. Following Shakyamuni’s enlightenment, four more realms outside the bounds and bonds of samsara were recognized: those who hear the Dharma (sravakas); those who understand the Dharma (pratyekabuddhas); bodhisattvas; and Buddhas.
In the hub of the wheel are three animals: a pig, a snake, and a bird. They represent the three poisons of ignorance, attachment, and aversion.
The pig stands for ignorance; this comparison is based on the Indian concept of a pig being the most foolish of animals, since it sleeps in the dirtiest places and eats whatever comes to its mouth.
The snake represents aversion or anger; this is because it will be aroused and strike at the slightest touch.
The bird represents attachment (also translated as desire or clinging). The particular bird used in this diagram represents an Indian bird that is very attached to its partner.
These three animals represent the three poisons, which are the core of the bhavacakra. From these three poisons, the whole cycle of existence evolves. In many drawings of the wheel, the snake and bird are shown as coming out of the mouth of the pig, indicating that aversion and attachment arise from ignorance. The snake and bird are also shown grasping the tail of the pig, indicating that they in turn promote greater ignorance.
Under the influence of the three poisons, beings create karma, as shown in the next layer of the circle.