The Wheel of Life is a mandala - a complex picture representing the Buddhist view of the universe.
To Buddhists, existence is a cycle of life, death, rebirth and suffering that they seek to escape altogether.
The six major sections represent the Six Realms.
In each of the realms, the Bodhisattva Avalokiteshvara appears to show the way to liberation from the Wheel. But liberation is possible only in the human realm. From there, those who realize enlightenment find their way out of the Samsara.
The creature holding the Wheel of Life in his hooves is Yama, the wrathful dharmapala who is Lord of the Hell Realm.
Six realms are:
Gods Realm - is the highest realm, but isn't perfect. The catch is that because the Devas have such rich and happy lives they don't recognize the truth of suffering. Their happiness is, in a way, a curse, because they have no motivation to seek liberation from the Wheel.
The realm of Asuras - is marked by paranoia. They are driven by a desire to beat their competition, and everyone is competition. Asuras, who are also called "anti-gods," are perpetually at war with the Devas of the God Realm.
Hungry Ghost Realm - have huge, empty stomachs, but their thin necks don't allow nourishment to pass. They are constantly hungry. Greed and jealousy lead to rebirth as a Hungry Ghost.
The Hell Realm - is marked by anger, terror and claustrophobia. Fiery Hell Beings are angry and abusive, and they drive away anyone who would befriend or love them.
The Animal Realm - They cling to what is familiar and are disinterested, even fearful, of anything unfamiliar. The Animal Realm is marked by ignorance and complacency.
The Human Realm - is marked by questioning and curiosity. It is also a realm of passion; human beings (Manushyas) want to strive, consume, acquire, enjoy, explore. Here the Dharma is openly available, yet only a few seek it. The rest become caught up in striving, consuming and acquiring, and miss the opportunity.
At the center of the Wheel of Life are the forces that keep it turning — greed (cock), anger (snake) and ignorance (pig).
These are the forces that keep the Wheel of Life turning, according to the Buddha's teaching of the Second Noble Truth.
The three poisons are the energy of ego’s three basic attitudes—for me, against me, and don’t care. All unwholesome states of mind (kleshas) are variations on these three themes. Because the poisons drive our suffering, they are traditionally depicted as three animals—a rooster, snake, and pig—at the center of the wheel of life.
Passion (also called attachment, greed, or lust): Whatever feels good we want more of. Above all, ego is attached to whatever ensures its survival—physically, psychologically, or spiritually. At the same time, passion has in it the seeds of love and connection, and so of the three poisons, it offers the best path to enlightenment.
Aggression (aversion, anger, hatred): We try to repel anything we believe will hurt or threaten us. Because we are willing to hurt others to protect ourselves, even on a massive scale, aggression is the greatest cause of suffering. In the Vajrayana school of Buddhism, its energy is seen as wisdom when self-interest is removed.
Ignorance (indifference): If you’re not for me or against me, you don’t matter. This is not the basic ignorance of solidified, dualistic reality that is the foundation of samsara, but it is what enables people to prioritize their own pleasure over the suffering of billions of others. There is no real potential for enlightenment in this indifference.