Christos (Christ) is the Greek translation of the Hebrew mashiach (Messiah), and both mean “the anointed one”. Initially it referred to anyone or anything consecrated with holy oil; for example, King David, unleavened bread, or King Cyrus.
For what a 1st century Jew would have understood as “the messiah”, see Messiah and Messiah in Judaism:
In Jewish eschatology, the term came to refer to a future Jewish king from the Davidic line, who will be “anointed” with holy anointing oil, to be king of God’s kingdom, and rule the Jewish people during the Messianic Age. In Judaism, the Messiah is not considered to be God or a pre-existent divine Son of God. He is considered to be a great political leader that has descended from King David. That is why he is referred to as Messiah ben David, which means “Messiah, son of David”. The messiah, in Judaism, is considered to be a great, charismatic leader that is well oriented with the laws that are followed in Judaism. He will be the one who will not “judge by what his eyes see” or “decide by what his ears hear”.