What does Haggai 1:1 mean?

On the first day of the sixth month in King Darius’s second year, the Lord spoke through Haggai the prophet to Zerubbabel (the governor of Judah) and Joshua (the high priest). Haggai 1:1 - Modern Text Bible

(This sets the scene: God’s message comes at a specific time to the leaders responsible for rebuilding Jerusalem.)