In the literal sense. The territories that form Palestine and the West Bank today were part of Egypt and Jordan before the six-day war. Israel occupied these territories during the war, then signed peace treaties with the countries it defeated. The three Arab countries (including Syria) attempted to recapture their territories again in 1973, but failed, and peace treaties were again signed between all four countries involved.
In the meantime, people living in the territories occupied by the Israeli military forces continued their fight for freedom, as all occupied people do. They made some strides in this direction with the Oslo accords, where they gained official recognition as a separate country under their own authority.
While open hostility existed on both sides since the beginning, there has never been an official war declaration between the PLO and Israel. Both have been routinely attacking and killing civilians and destroying infrastructure in each other's country forma long time - though Israel now has a vast upper hand and the killing and destruction has become more and more one sided against the people of Palestine.
