The Tripitaka (Sanskrit for "three baskets"; "Tipitika" in Pali) is the earliest collections of Buddhist scripture. There are several versions, the oldest and most complete of which is called the Pali Canon because it is in the Pali language.
It is believed the many texts within the Tripitaka are the words of the historical Buddha as memorized and chanted by generations of monks. It was not written down until about the 1st century BCE.
The texts of the Tripitaka are organized into three major sections -- the Vinaya-pitaka, containing the rules of communal life for monks and nuns; the Sutra-pitaka, a collection of sermons of the Buddha; and the Abhidharma-pitaka, which contains interpretations and analyses of Buddhist concepts. In Pali, these are the Vinaya-pitika, the Sutta-pitika, and the Abhidhamma.
For historical background on how the Tripitaka came to be written, please see "The First Buddhist Scriptures: The Tripitaka or Pali Canon."