After the death of Solomon, the kingdom split into the Kingdom of Israel in the north and the Kingdom of Judah in the south. The Kingdom of Judah was composed of the tribe of Judah and the tribe of Benjamin.
Unlike the Kingdom of Israel, which frequently saw changes in its dynasty, the Kingdom of Judah maintained an unbroken dynastic line.
It was destroyed by the invasion of the Babylonian Empire.
In many prophetic books, it is referred to like a person's name, ultimately used as a pronoun to collectively refer to God's people.
[See Genealogy of the Kingdom of Judah]