What does 1 Kings 12:20 mean?

When everyone in Israel heard that Jeroboam was back, they called everyone together and made him king over all Israel. Only the tribe of Judah stayed loyal to David’s family. 1 Kings 12:20 - Modern Text Bible

(Jeroboam becomes king of the northern tribes, while Judah alone remains with the Davidic dynasty. This is the official start of the divided kingdom.)