The Wheel of Life thangka is also known by the name of Bhavachakra thangka or the Wheel of Samsara. Bhava means the world where you live in and chakra means the wheel that moves in your life. Just like the wheel moves, people also move. Samsara means the cycle of birth.
There are four circles of Bhavachakra. Inside the smallest circle, you will see three animals. They denote lust, infatuation, attraction, ignorance, dullness, greediness, desires, anger, wrath, the characteristics of an evil person, etc. Lord Buddha says human beings possess the characteristics of these three animals.
If you want to attain Nirvana, then you got to free yourself from these characteristics. The smallest circle is surrounded by another circle which you can call the third largest circle (that will be easy for you to understand), where you see human beings going towards the direction of the sky and other human beings going down towards hell. The white color denotes good deeds, and the black denotes the deeds of an evil person.
Wheel of Life or Samsara (Bhavacakra) Thangka