A big change happened to the Israelites when they went from a society run by wise men (known as Judges, like Deborah and Samuel) to a society with a King. They wanted to be like the other nations of the world and the people asked Samuel to appoint them a King. The first King was King Saul. He was killed in battle, and the next two Kings were more famous, King David and his son King Solomon. King David was a warrior who united the country like no one had before. You might compare his role as similar to the United States adopting the Constitution and becoming one country.
A huge change came when King Solomon built the Holy Temple in Jerusalem. The Holy Temple was considered the home of God. It was very sacred and only Priests were allowed into it. Everyone else stood on the outside and watched.
In those days, the people believed in animal sacrifice and the rule became that animals could only be sacrificed at the Holy Temple. So people in the outlying areas of Israel had to go to Jerusalem if they needed to make an animal sacrifice. There were all kinds of sacrifice – some were for sins, some were for having prayers answered, some were for ritual.
King Solomon lived a very high life, and had thousands of wives and other attributes of wealth. To live this lavish lifestyle, he had to collect heavy taxes from the people. The tribes located farther away grumbled under the tax burden, and after King Solomon died, his son who succeeded him as King refused to lighten the load. Therefore, the tribes in the north (known today as the Ten Lost Tribes) seceded from the union and formed their own country, much as the South tried to do in America. Unlike America, however, there was no civil war, and the Ten Tribes succeeded in forming their own country, which they called Israel. The only tribes left to the heirs of Kings David and Solomon were the large tribe of Judah and part of the tribe of Benjamin. That country was called Judea (and their citizens were called Judaeans, which over time became Jews).
Eventually the Kingdom of Israel was conquered by the Assyrians and most of the people there were led off into exile, never to be heard from again. The same thing should have happened to the Judaeans when they were conquered by the Babylonians and led off into exile, but because their Judaism was able to change in a big way, the Judaeans did not disappear.
