Zechariah was a prophet (holy man). The Book of Zechariah is in the Old Testament part of the Bible.
Zechariah lived at the same time as Haggai. God showed Zechariah many strange pictures to encourage the people in Jerusalem. These pictures explained good things that God would do in the future.
Zechariah wrote about some things that would happen during his own life. And we now know that Zechariah wrote some things about Jesus. Jesus is both a priest and a king (Zechariah 6:12-13). Zechariah describes Jesus' death in Zechariah 12:10.
Some things that Zechariah described have not happened yet (Zechariah 14). These things will happen in the future.