Vimalakīrti is a contemporary of Gautama Buddha and an ideal buddhist. He was extremely rich and wealthy but he was equally rich in wisdom. None of Buddha's disciples could match his wisdom.
Vimalakirti manifested himself as sick. To inquire about his health, thousands of people came forth from the great city of Vaisali and Vimalakirti took this as an opportunity to teach them the Dharma and lead them to enlightenment.
Vimalakirti Sutra teaches the highest and deepest philosophy of nothingness, the appearances of the world as mere illusion, defines what enlightenment means, proves the nonexistence of any kind of self or individual identity.
This is one of the best sutras of Buddhism. One who learns and understands this sutra is definitely on his/her way to the highest state of true wisdom.