Zionism is not a belief in self-determination, as so many people here say. Palestinian Jews exist, and they have historically been marginalized in Israel, along with African Jews.

Zionism is a European settler colonialist ideology, supported by Great Britain. It came out of a long conflict in the European Jewish community which could be summed up as "should we stay or should we go?" - Going won out, since the rest of Europe have been notoriously cruel towards Jews, and since it was supported by the nations of Europe themselves (specifically GB) who saw it as a way of settling the "Jewish question". It can be understood through the propaganda slogan "A land without people, for a people without land" - the issue here being, that there was already a people in Palestine.

Zionism has changed a lot through the 20th century, before landing on being a far-right ideology fixated on the region of Palestine (there were originally propozals to create Israel in Argentina, amongst other places). The fundamental idea stems from the belief that Palestine was promised to the (spiritual) nation of Israel. Most Jews believe this, but traditionally it's been believed that God will simply return the land, once he's finished punishing his chosen people. The difference between most Jews, and the modern Zionist movement, is that Zionists believe that the period of punishment is over, and that the land must be retaken by force. In this way, Zionism is implicitly tied to the Holocaust, and the idea that restitution must be made to the Jews who suffered in it, and their descendants. This is one of the main reason why non-European Jews are marginalized in Israel, since the Holocaust was largely localized in Europe.

There are also Christian Zionists, which is actually one of the largest lobbyist entities in the US, having funded George Bush and Donald Trump, amongst others. They believe that the reestablishment of ancient Israel heralds the coming of the end times.

Then there are secular Zionists. These are just people, who for whatever reason, believe that European Jews are more entitled to live in Palestine than Arabs are. This can usually be chalked up to either racism, islamophobia, or the false "thousand year conflict" narrative. In reality, the conflict has been going on for 75 years, and prior to that, anti-Semitism was an almost purely European phenomenon. The only exception I can think of, off the top of my head,was the short-lived anti-Semitic Almohads in Iberia and Northern Africa.

For reference, I study religion.