He is an incarnation of god Vishnu. He is known as Veda-vyasa as he divided the complex veda-rasi (voluminous single Veda) into four Vedas (Rigveda, Yajurveda, Sama veda and Atharva veda), for the convenience of people so that people will easily understand them. He also compiled the 18 Puranas and the Maha-bharata, the story of battle of Kauravas and Pandavas and he also figures in this story actively.
Also known as Paarasarya (son of Parasara), Krishna-dwaipayana (one born in Krishna-dweepa) and Saatyavatheya (son of Satyavathi). His service to mankind is unparalleled as he devoted his entire life for propagation of Dharma (righteousness) by seggregation of Vedas, compiling of Bharata, Bhagavata and Puranas.
According to some Puranas, ‘Vyasa’ refers to a title rather than name of a person. In every Dwapara-yuga (3rd out of the four Yugas or ages viz., Krita, Treta, Dwapara and Kali), one great saint will assume the title of ‘Vyasa’ to propagate Dharma. Krishna-dwaipayana was the Vyasa in previous Dwapara-yuga. In the coming Dwapara-yuga, Aswathama (a hero in Mahabharata war and son of Drona) will be the Vyasa.