The Israelis and Palestinians are fighting over the same land because they both think it's The Holy Land. The Palestinians had laid claim to it for hundreds of years (I think) and then the state of Israel took over the same land in 1950, which of course pissed off the Palestinians. Fighting ensued. The US, which is a massive military power backed the Israelis (because we have a bunch of Jews/Israelis with very deep pockets), which pissed off the Palestinians even more.
This is a vast oversimplification of about 70 years of massacres, death, and hatred on both sides. For the past 20 years or so, Israel has been incredibly brazen in its destruction of Palestine and colonization of Palestinian lands. At the same time, Palestine is literally controlled by a terrorist organization that is not even trying to attack military targets and instead seems set on some sort of vengeance (while using Palestinian citizens as human shields). So neither are good, and both seem set on genocide. If you had to pick one, stand with Palestine but denounce Hamas.