The book of Hebrews (the New Testament epistle, if you were second-guessing) in its first three verses begins by stating the two ways by which GOD is revealed to humanity.
Revelation by the created; not creating
This refers to the various media which are part of creation that show forth the eminence of the CREATOR: the inanimate and the animated forms of life in nature and other spheres of existence. However, this also covers humans: ordained by GOD to represent HIS interest and intentions on the earth. It is in this category that you shall find Prophets and the prophecies which they give. These prophecies are messages, given to (wo)men from GOD through prophet(s).
For the Coming of the Messiah, the prophets were used as pointers, as directions (I dare say tour-guides) who left bits of the puzzle that once they (puzzle pieces) were all collected they could point to one person: The MESSIAH.
The roles of the prophets were: to keep the hope for the Messiah alive; ensure that the sculpting by the law was in effect; and warned against leaving GOD which is the greatest evil to be committed. Yet the duties of the prophet are beyond this list but the emphasis of this bond is the role of the prophet to give a description narrative of/to the Messiah.
This is best explained in this scenario:
A poor beggar was told the Governor was very keen on helping him get better in life and would one day send one of his assistants to give him money and a job. He was told that tar assistant would come by afternoon but no certain time and date was given so the beggar had to be on the look out after noon everyday.
Furthermore, he could be sure of who it was because the assistant would be wearing a white shirt and black corduroys with a pink hat and a golden glove and when he spoke, he would sound like a trumpet. Now even if many men walk passed the pavement, the beggar-man would be expectant to see a man fitting those qualities.
That’s how the prophecies were/are: each prophet had a very special duty of adding better pixels to the imagery of the Messiah so that when the Messiah came, we could all be sure that this…was the Messiah.
The prophets and prophecies were and are directions to the coming of the Messiah (both as a Lamb to be slaughtered and the Lion, triumphant).
They are brush-strokes to the portrait of the Messiah, giving a certification of surety (as well as colour from the palette of GOD’s redemptive plan) on the person of the Messiah by leaving details to indicate that the Messiah is the Messiah.
It all shows that GOD has had this all planned. The coming of the Messiah was not by accident or a result of a gambling with stars. It was the best evidence of predestination, a projection into the new creation by redemption from sin to the sincere work of repentance unto salvation which pays us the wage of life with GOD, forever.
Revelation by the Creating; not created
The second Way GOD is revealed to humanity is by the creating not created. This medium is where GOD uses HIMSELF to present HIMSELF to us and this is one category with the best instance as JESUS CHRIST: The Messiah who is GOD and heir to all that is. Amen.