Haggai was a prophet (holy
man). He lived at the same time as Zecharaiah. Then, some people from Israel had returned from Babylon. They rebuilt their own houses in Jerusalem. Haggai
explained why they were poor. He said that God was not blessing them.
Haggai told them that they
should also rebuild God's temple (the house of God) - Haggai 1.
The new temple was small.
But God told Haggai that it would be greater than the old temple (Haggai 2).
And now, God would bless the people because they had rebuilt the temple.