The Buddha then turned the wheel of Dharma a second time at Vultures' Peak in India, with the emphasis this time on prajna. "Prajna" is a Sanskrit word, also called prajnaparamita, which in Chinese is translated as Zhi hui du. "Zhi hui” means (transcendent) wisdom; du means crossing over to the other shore.
Every sentient being is endowed with wisdom, but our wisdom is limited in depth and scope because we lack proper training of the mind. Zhi hui du refers specifically to the training of the mind, to cultivating the wisdom that allows us to reach the unsurpassed state of attainment — Buddhahood. From the view of an outsider, the process appears to be mysterious and connected in some way with religion; however, a true practitioner knows this training of the mind is very real. The sutras most people are familiar with, such as the Heart Sutra and Diamond Sutra, as well as many Ch'an discourses belong to the second turning of the wheel of Dharma. The teachings of the second turning are likened to courses given in secondary school.
~ Depicted from ARE U READY FOR HAPPINESS : The Significance of Buddhist Philosophy Today