Nakba (Arabic: النكبة, "al-Nakbah") is a term used to refer to the expulsion/migration of over 700,000 Palestinians from Mandatory Palestine. While the Israeli government officially claims there were no expulsions and most Palestinians claim nobody left of their own accord or on command of Arab leaders and armies, the truth is probably somewhere in the middle. What exactly is the truth is a hot button issue for all involved and even many uninvolved people. Today around 6.5 million descendants of those people who left mandatory Palestine in 1948 live in refugee camps all over the Middle East, only rarely integrated into mainstream society and granted equal rights.
The "right of return" for those people is a frequent point of contention in negotiations. While most Palestinians think there should be a right even for descendants born in refugee camps to return to the home of their forebears, Israel mostly maintains that refugee status cannot and should not be inherited and if anything a "right of return" could be granted to (some of the) people who personally left what is now Israel as part of a comprehensive peace deal. Interestingly, the question of how many people actually want to return is hardly ever discussed.
- https://www.washingtonpost.com/news/worldviews/wp/2012/11/30/palestinians-israel-settlements-arab-countries-refugees/ Contains an account of the treatment of Palestinian refugees in Arab countries
- http://zochrot.org/en/article/52138 Statement on the Nakba and the Right of Return