The Jataka

Jataka, (Pali and Sanskrit: “Birth”) any of the extremely popular stories of former lives of the Buddha, which are preserved in all branches of Buddhism. Some Jataka tales are scattered in various sections of the Pali canon of Buddhist writings, including a group of 35 that were collected for didactic purposes. These 35 constitute the last book, the Cariya Pitaka (“Basket of Conduct”), of the Khuddaka Nikaya (“Short Collection”). Beyond this, a Sinhalese commentary of the 5th century that is questionably attributed to a Buddhist scholar named Buddhagosa and called the Jatakatthavannana, or Jatakatthakatha, gathers together about 550 Jataka stories, some of which are quite brief while others are as long as novelettes.

Each tale begins by noting the occasion that prompted its telling and ends with the Buddha identifying the lives of the people in the introductory story with those of people from the past. There is humour in these stories and considerable variety. The future Buddha may appear in them as a king, an outcast, a god, an elephant—but, in whatever form, he exhibits some virtue that the tale thereby inculcates.

Many Jatakas have parallels in the Mahabharata (“Great Epic of the Bharata Dynasty”), the Panca-tantra (animal fables), the Puranas (collections of legends), and elsewhere in non-Buddhist Indian literature. Some turn up again in such places as Aesop’s fables. The Jataka stories have also been illustrated frequently in sculpture and painting throughout the Buddhist world.

Source:
http://www.britannica.com/EBchecked/topic/301580/Jataka