According to Genesis, the Jews are the descendents of the Patriarch Jacob, to whom God gave the name "Israel." Because of this, Jacob's twelve sons were called the "sons of Israel." Thus the term "sons of Israel" or "Children of Israel" is meant literally. In English, we often use the term "the people Israel" to designate them and their descendents. Jacob's twelve sons were named: Reuben, Simeon, Asher, Levi, Judah, Issachar, Naphtali, Gad, Benjamin, Dan, Zebulun and Joseph. All of them, except for Joseph, became the heads of tribes; Joseph's two sons, Ephraim and Manasseh, also became the leaders of tribes. The latter two tribes are called "half-tribes" so that the number of tribes will work out as twelve. However, since Ephraim and Manasseh were the second and third most numerous and powerful tribes (after Judah), there were really thirteen tribes.
The tribes were important only during the Patriarchal Period. As soon as the monarchy was established by David, steps were taken to reduce the tribes' power. After the split into the northern Kingdom of Israel and the southern Kingdom of Judah in 932 bce, ten tribes were in the northern kingdom, while three tribes (Judah, Benjamin, and Levi) remained in the southern. With the destruction of the northern kingdom and the deportation of its inhabitants in 721 bce, these ten tribes were essentially lost to history.
After this point, when the residents of Judah are referred to citizens of a nation or province, they are called Judahites, or later, Judeans. If they are referred to in religious terms, they are called the people Israel (Israelites) or generally as Jews. (The term "Jew" derives from the Latin word for "those who live in Judea.")
The tribe of Levi, known as Levites, retained its identity because God assigned its members to run the Temple. Most of the tribal members had support jobs as guards, muscians, janitors, wood-cutters and so on. But one family, known as Cohen, served as the priests, performing sacrifices, offering incense to God and related tasks. There are Jews even today whose last names indicate that they believe they can trace their lineage back to the Levites (e.g., Levi) or the Cohens (e.g., Cohen, Cohn, Kahana, Cahane, etc). This is surprising, given that with the destruction of the Temple, they were left with few special duties and no special status.
When the destruction of the Temple in 70 ce deprived the priestly class (the Cohens) of their base of power, the rabbis rose to replace them. A rabbi was a teacher; the term means "my master," a sign of respect said by a student or disciple to his teacher. Over the next few centuries, rabbis served not only as teachers, but also as lawyers and judges, helping the Patriarch (the head of the Jews in Palestine) to govern. They created schools and academies, wrote books, and decided matters of religious, ethical and civil law. This system was recreated in the Babylonian diaspora in the third century ce, and the rabbis there wrote the Babylonian Talmud, which became the basis for Jewish belief, practice and faith up to the modern period.
The influence of the Babylonian rabbis was transcended by those in Spain around 1100. And the Spanish academies were active until 1492, when Queen Isabella and King Ferdinand decreed that Jews either had to convert to Christianity or leave the country. Most of the Spanish Jews who left went into the Moslem countries around the Mediterranean where they found refuge. It is at this point that an earlier distinction between the Jews in Spain and those elsewhere in Europe solidified. The Jews of northern Europe were called Ashkenazic Jews, while those who had been in Spain and left were known as Sephardic Jews. Communication between the two groups diminished significantly, and it was not until the founding of the State of Israel in 1948 that regular contact was reestablished, primarily through large-scale immigration of both groups to the state.
The Ashkenazic Jews continued their development uninterupted through this period. They were largely divided into two groups, those who followed the traditional practices and those who added mystical elements to them. The latter were called the Hasids or Hasidim. They drew upon mystical, kabbalistic writings like the Zohar and incorporated them into otherwise traditional practices and beliefs. (For an explanatin of Kabbalah, go here.) Many of the Hasidic groups exist today; there are several groups in New York City, where they are known for their black clothing and their wide-brimmed black hats. The Lubavitch Hasidim are best known, perhaps because of their missionary activities among Jews at college campuses.
With the beginning of the Enlightenment in the 1700s and then the Emancipation in the 1800s, Judaism underwent big changes. In central Europe (Germany and France), some Jewish thinkers began to argue that Jews needed to fit better into the societies in which they found themselves. In Germany, Jews were offered the opportunity to become citizens and many Jews transformed themselves and their religion so that rather than being "Jews living in Germany," they became "Germans of the Jewish Faith." This movement became known as Reform Judaism, because it reformed many of the traditional practices, behaviors and dress to fit better into German society. (For an official view of Reform Judaism and its faith, go here.)
Many other Jewish thinkers, particularly the traditionalists, argued strongly against this. They held that Jews and Judaism should not change, but should stick with the centuries of tradition that Jews had "always" followed. This group became known as Orthodox Judaism. (For a discussion of the different groups within Orthodoxy and their history, go here.)
In the early twentieth century, a third branch developed which became quite popular in the USA. This was Conservative Judaism. To over-simply its emphases, it could be said that in terms of Jewish practice, it followed the Orthodox, namely, keeping traditional ways. But in terms of belief, it was more like Reform, namely, open to change. (To explore some of the key beliefs of Conservative Judaism, go here.)
In the USA, Reform and Conservative Judaism have had the most followers, somewhere between 40 to 45 percent of the Jewish population each. Orthodoxy has been much smaller, with approximately 10 to 15 percent of Jews.
An even smaller division of American Jewry is Reconstructionist Judaism. This movement was founded in the 1950s. Its central tenet is that Judaism is primarily a cultural movement, rather than a religious one. Thus Jewish cultural and identity are important, but Jewish belief much less so.
No description of modern Judaism would be complete without discussing Zionism. Zionism can essentially be described as Jewish Nationalism, that is, the desire for the Jewish ethnic group to have their own nation in their own land where they can speak their own language, be in charge of their own political destiny, and practice their own culture without restriction. It began as an ideological movement in the latter half of the nineteenth century in Europe. By the end of the century, Jews were immigrating to Palestine to establish communities with a foothold in the "holy land." At this stage, Zionism was largely a secular ideology, and a means for rejecting much of religious belief. Only the Tanak was important because it provided the basis for seeing Palestine as the Jewish homeland. By the 1920s, large numbers of Jews had settled in Palestine, enough to begin to cause international political problems. But during World War II, the Nazis perpetuated what is now called the Holocaust, systematically killing over six million Jews, and rendering hundreds of thousands homeless. In 1948, the Zionists in Israel declared the creation of the Jewish state of Israel. They were immediately besieged by armies from several Arab countries. After weeks of fighting, Israel remained, holding more territory than they had originally claimed. At this point, they made it clear that they would take all Jews from Europe who wished to come. Indeed, they sent out a call for all Jews to return to Israel, which many Jews did. Tens of thousands of Jews came from the Arab nations, often being airlifted out just ahead of persecution. The Jews who live in the modern state of Israeli are known as Israeli (pl. Israelis).
Israelis claim the modern (and ancient) city of Jerusalem as the capital of Israel. It is here where the Temple was originally built by Solomon and ultimately destroyed by the Romans in 70 ce. (For pictures and history of Jerusalem, go here or here.) Although there are no remains of the Temple itself, portions of the platform that supported the Temple remains. One of the walls of this platform is known as the holy Wailing Wall . (For a LIVE view of the wall, go here. While there, be sure to check out the overhead view of Jerusalem [Heavenly Jerusalem] and find out how to send a prayer to the wall.)
Finally, one of the major organizing events of contemporary Judaism is the Holocaust. This happened during World War II, when Nazi Germany decided to do away with the Jews and other people they considered to be undesirable (like gypsies and Poles). Before the war was over, the Nazis managed to kill over six million Jews. For further information about the holocaust, visit the US Holocaust Memorial Museum's brief history of it.