What does 'Messiah' mean
Messiah is a word that comes from the Hebrew word Moshiach, which means The Annointed. The word Christ is the Greek version of Messiah, coming from the word Christos.
The need for a Messiah arose after the fall of man. When Adam and Eve ate the fruit on the Tree of Good and Evil in the Garden of Eden, their path to the Tree of Life was blocked. The first prophecy of a Messiah is found in Genesis 3:15: "And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel".
Moving on through the bible stories we find some criteria the the Messiah must meet:
The Messiah must be a descendent of Jacob - Numbers 24:17 "I see him, but not now; I behold him, but not near. A star will come out of Jacob; a scepter will rise out of Israel. He will crush the foreheads of Moab, the skulls of all the sons of Sheth.".
The Messiah must be a descendent of King David - Jeremiah 23:5-6: "Behold, the days are coming, saith the LORD, that I will raise to David a Branch of righteousness; a King shall reign and prosper, and execute judgment and righteousness in the earth. In his days Judah will be saved, and Israel will dwell safely; now this is his name by which he will be called: THE LORD OUR RIGHTEOUSNESS.
The main mission of the Messiah is to restore the relationship between Man and God to the state it was prior to Adam and Eve's sin of eating the fruit of the Tree of Good and Evil in the Garden of Eden.