Jews lived in Israel but during Roman period most of them were expelled out to Europe or Arab World. Those Jews who lived in Europe were called Ashkenazi. When Europe converted to Christianity these Jews were subjected to centuries of persecution. By the 7th century Arabs conquered Palestine. It was followed by crusades and Ottomon rule.
Theodor Herzl proposed a concept of Jewish homeland in their ancestral home Palestine to escape discrimination in Europe. In world war 1, Ottomons were defeated and British took control of Palestine. Although in 1800s many Jews started to settle in Palestine. After Holocaust and German surrender many European Jews started to arrive in British mandate of Palestine.
Arabs were not ready to accept the arrival of Jews. UN proposed two state solution in Palestine, Israel accepted it but Arabs rejected it. When British left war broke out with neighbouring Arab countries, Israel ended up in getting more land while Egypt got Gaza and Jordan got West Bank and East Jerusalem(which contain the Jewish religious site of Wailing wall). After that Jews in Arab world started to migrate to Israel(both by zeal and growing anti-Semitism in Arab world) while the Palestinian Arabs were living in different refugee camps of West Bank and Gaza.
In 1967, war broke out between Israel vs Egypt, Jordan and Syria. Arabs saw defeat as Israel conquered Gaza and Sinai of Egypt, Golan Heights of Syria and West Bank including East Jerusalem from Jordan. After few years Israel vacated Sinai. Another war broke out in 1974 and ended up without any territorial change.Israel call West Bank as Judea and Samaria as existed in ancient time. Israel later allowed self governance to Gaza and West bank called Palestinian authority.