The Ashoka Chakra is a depiction of the Dharma Chakra; a wheel represented with 24 spokes. It is so called because it appears on a number of edicts of Ashoka, most prominent among which is the Lion Capital of Ashoka. The most visible use of the Ashoka Chakra today is at the centre of the Flag of India (adopted on 22 July 1947), where it is rendered in a navy blue colour on a white background.
The 24 spokes represent the twelve causal links taught by the Buddha. The first 12 spokes represent 12 stages of suffering. Next 12 spokes represent no cause no effect.
So, due to awareness of mind, formation of mental conditioning stops.
This process stops the process of birth and death i.e. nibbāna. The twelve causal links, paired with their corresponding symbols, are:
Source: https://en.wikipedia.org/wiki/Ashoka_Chakra