This drawing of the wheel of cyclic existence has six sections in it; the upper ones depict the gods, anti-gods and humans while the other three depict the bad migrations within cyclic existence. They represent the levels of suffering. Due to what conditions do they arise? The inner circle indicates that these levels of suffering are produced by karma, ie. actions. It is in two halves, the left half depicting virtuous and unfluctuating actions and the right nonvirtuous actions leading down to the lower realms. Here the people on the left are facing upwards and the people on the right are facing downwards.
The source of suffering is karma, which arises from the afflictions of desire, hatred and ignorance, indicated by the innermost circle. The pig indicates ignorance, the snake indicates hatred and the rooster indicates desire. In a more correct version of the drawing, the rooster and snake would be coming out of the mouth of the pig, and they would have their mouths on the tail of the pig. This indicates that desire and hatred have ignorance as their root, but the fact that they in turn hold on to the tail of the pig indicates that they act to further and assist each other.
Thus the drawing shows that the three afflictive emotions of desire, hatred and ignorance give rise to virtuous and nonvirtuous actions, and these give rise to the various levels of suffering in cyclic existence. What then is the order of cause and effect for the arousal of such suffering? This is indicated by the outer ring, symbolizing the twelve links of dependent arising. This fierce being on the outside doesn't indicate a creator deity, he symbolizes impermanence. He shouldn't really have all these ornaments. Once, when I ordered a thangka like this, I had him drawn as a skeleton, as he represents impermanence. The moon indicates liberation. The Buddha is pointing at it, indicating that one should generate the paths that lead to liberation.
The history of this drawing is that the king of a distant land made a present of a jewel to the King of Magadha, and the King felt he did not have anything of equivalent worth to give in return, so he asked Buddha what he should give. Buddha told him to give a drawing like this of the twelve links of dependent arising, with the five sections symbolizing suffering. It is said that when the distant king received the picture and studied it, he attained realization from it.