The Jews lived there a couple thousand years ago. After world war 2 they were given the land as their own nation. Unfortunately, the Palestinians already lived their and still are not happy at how the Israelis took their ancestral homes from them.
Simplistic, but yes. Although the land given by the UN to the Jews was much smaller than what is now the state of Israel.
Israel is the ancient and ancestral homeland of the Jews.
It's more complex than that. I will use "Palestine" as the name for the region as a whole. Southern Palestine (Judea) is the ancestral homeland of the Jews. Northern Palestine is the ancestral homeland of the 10 Israelite tribes, many of whom became Samaritans (in Jesus' time, for example, Samaria was very much a distinct, non-Jewish region, and the Parable of the Good Samaritan deals with the hostility between Jews and Samaritans).
Following Alexander the Great's invasion, many Greeks settled in Palestine too, and archaeology shows many Greek towns from Jesus' time (the gymnasiums and pagan temples are the big clue).
Before the Jews, of course, there were Canaanites, and they hung on in Southwest Palestine (including Gaza, but also some cities now in the state of Israel).
In the centuries after Jesus, many Jews became Christian (so Bethlehem, for example, has been a Christian town for almost 2,000 years), and the whole of Palestine became a Christian country with a few Jewish and Samaritan settlements.
Following the Arab invasion, many Christian inhabitants of Palestine (including some descendants of former Jews and former Samaritans) became Muslim, and Arab settlers also arrived. Several Crusades tried and failed to kick the Arabs out, and left behind some people of part-European origin.
In addition, Jews have lived outside Palestine for a long time, in the so-called Diaspora. Even in Jesus' time, there were more Jews in Egypt than in Palestine. In addition, a great many Jews had never returned to Palestine from Babylon, but had lived there since the Exile. After 1948, however, Jews became unwelcome in Muslim countries and around a million were forced to leave -- in most cases, travelling to what is now the state of Israel, from lack of any other alternative.
People on all sides have suffered, but it's probably true that the conflict in that part of the world has been toughest on the Christians than on anybody else.