The Samaritans is a small ethnic and religious minority who claim to be the true religion of the ancient Israelites. ( For the differences between Israeli, Jew, Zionist, here)
According to the Samaritan version, the separation between them and the Jews happened during the times of the prophet Eli. The dispute was about the location of the chosen place for the temple. According to their belief, the sacred place is mount Gerizim. So there were 2 worship places at the same time, One in Jerusalem which was in the area of Judea (that is why the people who worshiped there were called Jews) and one worship place in Samaria (Shomron). they also see themselves as the descenders of the tribes of Ephraim and Menashe who didn’t go on exile.
They see themselves as the "true" Jews who never went to exile and therefore the real keepers of the traditions and laws.
According to the Jewish bible when the kingdom of Israel went into exile by the Assyrian king, other nations were brought to their lands as a population control method. You conquer a kingdom, expel their people to a location far away from their previews one. now the people will be concern about surviving and adjust to the new place instead of revolting.
The Israelites were exchanged with population from the area of what is today Iraq. As those people settled in the former land of the Israelites they were attacked by lions and disasters. Only after a Jewish priest came and taught them about the Jewish belief the disasters stopped, and they all converted to Judaism.
As the Jews came back from the exile they saw the Samaritans as others and not "real" Jews. They didn’t want them to take part in the construction of the second temple. since then there's a split between the 2 nations.
The Samaritans didn’t take part in the rebellions against the Romans, as the Jews went to exile (again...) the Samaritan population in the land increased and they spread out of Samaria. According to the Samaritans at those times their population were the majority in the land of more than 1 million people. The Samaritans revolted later against the Byzantine Empire as their situation got worse as the Roman Empire accepted Christianity. At some point, the Samaritan religion was banned and here is estimation that more than a million Samaritans died during those revolts.
Under the Arab rule, the Samaritan population decreased as they were forced to accept Islam and were massacred. At the 14th century, their numbers were around 500 and their community concentrated around Nablus which is next to mount Gerizim.
Islam sees the Judaism and Christianity as the religions of the book and in general, are allowed to live under Islamic rule for Jizya( a special tax). The Samaritans tried to convince the ruler Ibrahim Pasha that they also believers of Torah, but the Muslims who couldn’t read the ancient Hebrew didn’t believe them. The Samaritans asked for help from the rabbi of Jerusalem who assigned them with a letter that approves their claim. France and England also call for the Ottomans to protect the Samaritans. At this point of history, the Samaritan community was close to extinction. Their numbers were 150 people only in 1838.
With the establish of the state of Israel, some of the Samaritans settled in Holon, a city next to Tel Aviv. Today the majority of their community lives in Holon and the rest in Nablus. Their total population is around 800 people divided into 4 families. Their small numbers, the fact that they are marrying only inside the community and not accepting conversion, led to a lot of genetic diseases. It was decided by the community that Samaritan man will be allowed to marry a not Samaritan woman who will accept the Samaritan religion and traditions.
All the Samaritans have an Israeli citizenship, the ones who lives in Nablus also own a Palestinian one.