Isa 9:6 For unto us a child is born, unto us a son is given
The Hebrew word mashach, that we translate messiah, means anointed one. The Greek translation of the same word, christos, is our word Christ. Therefore, when you hear the English-speaking Christian talking of Jesus Christ, or Jesus the Christ, they are referring to their belief that Jesus is the Anointed One, or the Messiah as promised in the Old Testament.
The prophets of ancient Israel spoke quite often of the Anointed One. The significance of anointing is that it was a ceremonial sign of being set apart for a special purpose, and as a symbol of having God's power or approval. Ancient Israel's prophets, priests, and kings were all anointed for their respective duties within the nation. In a minor sense, each of these were anointed ones.
The future Anointed One, however, was specified by prophecy to come at a certain time, in a specific place, having a certain lineage, be called "Mighty God", accomplish specific tasks, suffer rejection and seeming defeat, yet establish a kingdom that would destroy all of its enemies. The Anointed One would rule this kingdom forever.