Judah refers to a person, a tribe, and a nation.
Judah, the person, was one of Jacob’s twelve sons.
Jacob’s descendants grew in number and became the tribe of Judah, one of twelve tribes comprising the nation of Israel. Each tribe settled in an assigned geographic area, which would be similar to a state or province today.
Later, when the nation of Israel was divided, the tribes of Judah and Benjamin, split off, forming a new nation that was known as the nation of Judah.