Tibetan Buddhist Wheel of Life~ Samsara Cyclic Existence 

Mantra- Extensive Prayer of The Pure Land .
Lama Nyima
The Wheel of Life is a traditional representation of the samsaric cycle of existence.
The diagram, said to be designed by Buddha himself, depicts an inner psychological cosmology that has had great influence throughout Asia. It is much like a map of the world or the periodic table of elements, but it is a map of an internal process and its external effects.
Dzongsar Khyentse Rinpoche writes:
It’s quite a popular painting that you can see in front of almost every Buddhist monastery. In fact, some Buddhist scholars believe that the painting existed prior to Buddha’s statues. This is probably the first ever Buddhist symbol that existed...One of the reasons why the Wheel of Life was painted outside the monasteries and on the walls (and was really encouraged even by the Buddha himself) is to teach this very profound Buddhist philosophy of life and perception to more simple-minded farmers or cowherds. So these images on the Wheel of Life are just to communicate to the general audience.
A Brief Explanation of the Diagram
The meanings of the main parts of the diagram are:
The centre of the wheel represents the three poisons.
The second layer represents positive and negative actions, or karma.
The third layer represents the six realms of samsara.
The fourth layer represents the twelve links of interdependent origination.
The monster holding the wheel represents impermanence.
The moon above the wheel represents liberation from the samsaric cycle of existence.
The Buddha pointing to the moon indicates that liberation is possible.
The Dalai Lama writes:
Symbolically [the inner] three circles, moving from the centre outward, show that the three afflictive emotions of desire, hatred, and ignorance give rise to virtuous and non-virtuous actions, which in turn give rise to levels of suffering in cyclic existence. The outer rim symbolizing the twelve links of dependent arising indicates how the sources of suffering-actions and afflictive emotions-produce lives within cyclic existence. The fierce being holding the wheel symbolizes impermanence...The moon [at the top] indicates liberation. The Buddha on the left is pointing to the moon, indicating that liberation that causes one to cross the ocean of suffering of cyclic existence should be actualized.
A Detailed Explanation of the Diagram
Centre of the Wheel: The Three Poisons
The centre of the Wheel of Life, featuring a pig, snake and bird representing ignorance, anger and desire
Ringu Tulku Rinpoche writes:
Tibetans have a traditional painting called the Wheel of Life, which depicts the samsaric cycle of existence. In the centre of this wheel are three animals: a pig, a snake, and a bird. They represent the three poisons. The pig stands for ignorance, although a pig is not necessarily more stupid than other animals. The comparison is based on the Indian concept of a pig being the most foolish of animals, since it always sleeps in the dirtiest places and eats whatever comes to its mouth. Similarly, the snake is identified with anger because it will be aroused and leap up at the slightest touch. The bird represents desire and clinging. In Western publications it is frequently referred to as a cock, but this is not exactly accurate. This particular bird does not exist in Western countries, as far as I know. It is used as a symbol because it is very attached to its partner. These three animals represent the three main mental poisons, which are the core of the Wheel of Life. Stirred by these, the whole cycle of existence evolves. Without them, there is no samsara.
Second Layer: Positive and Negative Actions
The images in this layer vary in different paintings of the wheel. In the image shown here, the two half circles represent positive and negative actions, or karma, that are motivated by the three poisons of ignorance, attachment/desire and aversion/anger.
The half-circle on the right shows positive or virtuous actions. Such actions are the means for attaining lives in the three higher realms of the gods, demi-gods and humans.
The half-circle on the left shows negative or non-virtuous actions. Such actions are the means for attaining lives in the three lower realms of the animals, hungry ghosts and hell-beings.
Third Layer: Six Realms of Samsara
The third layer of the wheel depicts the six realms of samsara.
Fourth Layer: Twelve Links
The fourth layer of the wheel depicts the twelve links of interdependent origination.
The Monster Holding the Wheel: Impermanence
Jeffrey Hopkins writes:
The wheel in the centre of the painting is in the grasp of a frightful monster. This signifies that the entire process of cyclic existence is caught within transience. Everything in our type of life is characterized by impermanence. Whatever is built will fall down, whatever and whoever come together will fall apart.