Answer:
Jainism and Buddhism were both versions of Hinduism that broke away from the Vedic-oriented Hindu tradition in the 9th century BC. It was a reaction to Hinduism, in that it and Buddhism came about as a result of the fact that Brahmins had a stranglehold over the religion at the time (in their eyes). Even today, the only real difference between Jainism and Hinduism is that a) Jains take the concept of "ahimsa" (non-violence) more strictly than Hindus, and that b) the Vedas are not a central authority (although other scriptures like the Upanishads and Puranas still apply to Jainism).
In fact, the concept of "ahimsa" originated with Jainism, and passed into Hinduism very soon after. Mainstream Buddhism (which was eradicated by the Muslims who invaded India) was similar in this regard.