The Dharma-chakra or wheel of dharma is a widespread symbol used in south Asian religions such as Hinduism, Jainism, and specially Buddhism.
As a solar symbol it first appears on clay steals of the Indus Valley Civilization from 2500 BCE.
Nowadays you can find this symbol in many variants painted or graved on doors and gates through all Mongolia.
The wheel also might be associated with light and knowledge. The Buddha is said to have set the “wheel of Dharma” in motion when he delivered his first sermon. This “turning of the wheel” signifies a great and revolutionary change with universal consequences.
In his explanation of the term the Theravada Exegete Buddhaghosa explains that this “wheel” is primarily to be understood as wisdom, knowledge and insight.
The wisdom has two aspects:
The wisdom of self-realisation of the truth
The wisdom of proclamation of the truth.
In Buddhism, the cyclical movement of a wheel is also used to symbolize the cyclical nature of life in the world (also refereed to as the “wheel of samsara”)