The book of Zechariah is a record of the messages of the prophet Zechariah. As with most prophets, Zechariah’s message focuses on current events for the people of Israel, but also has a secondary meaning, anticipating the life of Jesus.
Zechariah was a contemporary of Haggai. The messages of both prophets concern the importance of rebuilding the temple.
Zechariah is sometimes called a minor prophet. This doesn’t mean he wasn’t important, but merely that the book named after him is shorter. (Compare this to the major prophets, whose books are much longer.)