This is correct, after Solomon the united kingdom split into the northern kingdom of Israel and the southern kingdom of Judah. The northern kingdom was the first to fall, with its 10 tribes being carried off into captivity (and thus into oblivion) or scattered. Some of these people fled to the south (archaeological evidence shows a sudden increase in Judah's population at the time the northern kingdom fell). Others fled elsewhere. Those who fled south blended with Judah's population, those who fled elsewhere or were taken captive disappeared from history. There are likely many people today whose ancestry could be traced in part back to these 10 tribes, and who don't even know it.
"Jew" is nothing more than the anglicized form of the word yehudi. It originally meant nothing other than someone from the tribe of Judah, but over time came to be used to refer to all Israelites. Think of it being similar to the way Hispanics use the term "Anglo" to refer to all people of northern European descent, regardless of their actual origin.
SD