Who are/were the Philistine Liberation Organisation (PLO) and who were they hoping to liberate?

Philistine is what some Arabic-speaking peoples call Palestine. The PLO has been called anything from a terrorist organization to an organization devoted to creating a separate Palestinian state, depending on the viewpoint. The UN recognizes the PLO. PLO hopes to liberate the Palestinian people as their name would suggest. The organization's headquarters in the Ramallah, West Bank. So far it's goals to "liberate Palestine" have come up short, marred by terrorist attacks and false propaganda.