Edit: Wrote this long ass message on my phone so expect errors. If you want I'd be happy to message further details tomorrow or continue discussion, but it's getting late now.
Well around the end of the 1900s a lot of Jews were having trouble in Europe because they generally weren't liked for a variety of discriminatory reasons. A group of somewhat radical Jews said fuck it, let's leave and go to where the Jews are said to come from and at the least we won't be persecuted by Europeans.
So they went and as more European Jews went a lot of non-European Jews began to go as well. At the time Palestine was a territory and the state that owned that territory eventually said it was ok if people want to move there.
In the 1920s Zionist Jews (not all of which were from Europe as many were also from the Middle East) accounted for ~11% of the population, but the general Arab sentiment was one of exclusion. During the early 1900s there were a variety of riots and revolts which seems to have mostly been by the larger Arab community against the Jews which resulted in the establishment of early Jewish militias which struck back.
Between the early 1920s and the late 1930s a number of these riots led to widespread massacres of the Jews by Arabs (there are so many individual events we could make a separate post). The Jews who remained got really really violent back.
The British government at the time spent a lot of time trying to make Arabs happy, get them to stop killing the Jews, get the Jews to stop killing the Arabs back, and the limit the immigration that was ongoing.
Eventually we get to 1936 and the first stage of the Arab Revolt which was against British control. The revolt sought Arab independence of Palestine and an end to Jewish immigration.
Eventually Great Britain was having enough of the situation and said we're out. They proposed the Peel Commission which proposed setting up two states, one for the Jews and one for the Arabs. In general the consensus is that the Jews either supported or were at least not against this plan. The Arabs on the other hand were vehemently against it and the revolt resumed in even greater force which lasted two years.
Finally Great Britain said fuck it, we're tired of this and these Jews don't want to leave (and to be frank they weren't crazy about having them return either). The Jews at this point were in active conflict with the Arabs at this point, religious leaders organizing people getting rounded up and murdered. The Jews stopped playing around and started doing crazy shit like blowing up markets and the like in relatiation (remember they are out numbered something like 9:1). Towards the end of the 1930s growing Nazi sentiments caused further migrations which led to the Jewish population rising to ~30% and the aid of British forces and foreign arms stopped the riots and turning the advantage to the Jews in combat.
After WW2 Britain really wanted out and for real this time, they tried to negotiate a split state and a peaceful withdrawal. It would have been a roughly 50/50 split that probably disproportionately favored the Jews (they only owned like 10% of the land prior to this). This was called the UN Partition Plan for Palestine. Neither side could agree so Great Britain just left. As this UN plan was being discussed Arab violence was starting to pick up, some buses full of Jews were bombed and a civil war broke out. On the last day of British control the Jews declared the state of Israel and the Arab Palestinians said oh no you don't. Israel was pretty much beating the Palestinian Arabs when suddenly the surrounding Arab states decided to invade Palestine. Some of the Jews were worried about wholesale slaughter (they had just gone through the Holocaust) and some Arab leaders were saying they were going to kill all the Jews.
Well, Israel won and quickly took over not just the part the partition plan would have given them, but also the Palestinian portion as well.
In the late 1960s there was another war between the Arab states and Israel which went much the same way as the previous one. Some state leaders were saying they would destroy all of Israel and the Palestinians thought that was a cool idea. Israel won and wasn't to happy with Palestine about this.
At some point Israel offered a one state system that would allow Palestinians to become citizens, but it was either difficult to complete (due to many missing records due to all the turmoil) or just outright rejection.
Eventually Palestine was allowed to elect it's own government (sort of) to operate within Palestine and Hamas won. Hamas is a terrorist organization that has the states goal of destroying Israel. Israel didn't like that.
People look at the Israel-Palestine situation and say Israel is wrong, but Israel is literally surrounded by countries who have it as their constitutional goal to destroy them. The Palestinians are being treated horribly, but looking back the violence was mostly begun by Palestinian leaders murdering Jews. When Israel has tried to give Palestine a break Palestine generally spits in their face and elects terrorist leaders. It'd be one thing if Palestine would tell it's neighbors to leave Israel alone and promise to stop declaring death to Israel, but whenever they get the chance the elect another terrorist.