This ring represents movement between the realms. Beings are shown rising and falling through the processes of karma and rebirth. All beings have been wandering around the wheel since begingless time.
The Buddha saw this process in a vision on his night of enlightenment;
With the Divine Eye, which is purified and surpasses the human, I saw beings passing away and reappearing, inferior and superior, fair and ugly, happy and unhappy in their destinations. I understood how beings pass on according to their actions: "These worthy beings who were ill-conducted in body, speech and mind, revilers of Noble Ones, wrong in their views, giving effect to wrong view in their actions, on the dissolution of the body, after death, have reappeared in states of privation, in an unhappy destination, in perdition, even in hell; but these worthy beings, who were well-conducted in body, speech and mind, not revilers of Noble Ones, right in their views, giving effect to right view in their actions, on the dissolution of the body, after death, have reappeared in a happy destination, even in a heavenly world."
(Majjhima Nikaya 36)