Rishi Veda Vyasa is a Hindu figure of yore, a divine guru, a luminary of spirituality whose status in Hinduism is equal to that of the gods and goddesses. Appearingly anachronisitically in numerous texts from the classic to early Modern period of Hinduism, he plays an important role in not only the literature but the belief of many Hindus. His name means "splitter," as in "Veda Vyasa," or "Splitter of the Vedas," a feat that, according to Hindus, allowed mere mortals to comprehend the grandeur of divine knowledge.
He divided the Vedas into four parts for comprehension for mankind and is also purported to have written the Mahabharata, all eighteen Puranas, especially, the Bhagavata Purana and said to have written the Brahma Sutras, an important Vedantic text that reconciled seemingly contradictory verses of the Upanishads. The Upanishads appeared to have contradictory verses but he showed through the Brahma sutras that they are not. Additionally, he is a secondary avatar of Vishnu.
He is also known as Krishna Dvaipayana (the dark one born on an island) and in modern Indian languages is known as Rishi Veda Vyaas or, more simply, Vyaas.
Like Hanuman, he is said to be immortal and is one of the seven Chiranjeevin.
Vyasa: a 'history'
By most accounts of yore, Vyasa was the grandfather of both the warring parties of the Mahabharata, the Kauravas and the Pandavas. He is also the narrator of the story and is said to have asked Lord Ganesh to aid him in writing it down for posterity. The story goes that Lord Ganesh imposed a condition that Vyasa narrate the story without pause, and Vyasa a counter-condition that Lord Ganesh understand the verse before he transcribed it. This is supposed to explain the complicated Sanskrit used in the Mahabharata.
Vyasa was the son of Satyavati, a ferryman's daughter, and the wandering sage Parashara. He was born on an island in the River Yamuna. The father of the princes Dhritarashtra and Pandu (by Ambika and Ambalika, the wives of King Vichitravirya), he also had a third son, Vidura, by a serving maid.
According to some accounts he is supposed to have sectioned the Vedic scriptures into appropriate format for the rest of humanity. His knowledge was supposed to be unique and whatever he knew could only be partially learnt by anyone else, whether by meditation, study of the vedas, fasting, self improvement, etc.
He is deemed to be the ideal Brahmarishi, omniscient, truthful, purest of the pure and possessor of knowledge of the essence of Brahman.
A sage also named Veda Vyasa (ca. 650-850), obviously deriving the name from the more mythic rishi, wrote the oldest extant and most influential commentary on the Yoga Sutras of Patanjali called Yoga-Bhashya.