The Palestine Liberation Organisation (PLO) was launched by the Arab League in 1964 as a Palestinian government-in-exile. It was granted observer status by the United Nations General Assembly in 1974, and became a "non-member observer state" (comparable to the Vatican) in 2012.
The Palestinian National Council (PNC) serves as the parliament for the whole worldwide Palestinian community.
Yasser Arafat was chairman of the PLO from 1969 until his death in 2004. He was succeeded by Mahmoud Abbas (also known as Aby Mazen).
In 1971 ("Black September") Jordan expelled the PLO to Lebanon. In 1982 Israel invaded Lebanon, and the PLO fled to Tunis.
The 1993 Oslo Accords created the Palestinian Authority (PA), to represent the Occupied Palestinian Territories as distinct from the worldwide Palestinian community. Mahmoud Abbas is now the leader of Fatah, the PLO and the PA, despite the fact that in the last parliamentary election in 2006 Hamas gained more votes than Fatah.