The concept of the Messiah is a significant one in both Judaism and Christianity, but I think it was in my Apocalypse class in college that I learned what it actually means, and how the concept developed, particularly in the context of eschatology. The Hebrew masiah simply means “anointed one,” and was used to refer to those who were anointed with oil to signify that they were chosen by God to fulfill a certain role, specifically king or high priest.
It was famously applied to a non-Jewish figure, Cyrus the Great of Persia.
After the Babylonians conquered Judah and destroyed the Temple, the Persians in turn conquered them and allowed the Jews to rebuild it. Cult leader David Koresh named himself after Kings David and Cyrus. I don’t think Billy Ray and Miley are involved in any of this, but you never know. Anyway, it seems to have been later in the Second Temple period that the coming of a future king known as THE Messiah, or Messiah King, would arrive to usher in a new Messianic Age, when peace would prevail and other nations would turn to Yahweh.
Historically, this is likely to be related to how, while both the Persian and early Greek rulers largely left Judea to its own devices as long as they paid the proper tribute and all that, Antiochus Epiphanes enforced brutal treatment on the vassal state, which led to the successful revolt of the Maccabees. Basically, things were so terrible that they thought a God-given leader would be necessary to set them right, a belief that shows up pretty often. This would be a new king from the line of David. There’s likely some Zoroastrian influence here, as that religion teaches of a future savior who would help in Ahura Mazda’s final defeat of his evil counterpart, Angra Mainyu.
In Daniel 7, there’s a reference to “one like a son of man” who would rule an everlasting kingdom after the collapse of several temporary ones. While there have been different interpretations of this, the phrase “Son of Man,” which technically just means a human being, came to be another title for the Messiah. This can be seen in the Book of Enoch, which posits that the coming Messiah would be Enoch himself returned to Earth. It was also a title Jesus used. To his followers, he was obviously the promised Messiah, and “Christ” is the Greek version of the title.
Of course, there was nothing in earlier belief about the Messiah dying before he could accomplish his purpose. It also wasn’t typical Jewish belief that the Messiah would be born of a virgin (which might also have Zoroastrian roots) or would be the literal son of God, both pretty important signifiers of Jesus’ supernatural status. And while being a descendant of David and born in David’s hometown of Bethlehem were common beliefs about the Messiah, but Jesus isn’t said to have really talked about those things, except for one passage in the Gospel of John where he says it doesn’t matter where the Messiah was born. Matthew and Luke both came up with ways for Jesus to have been born in Bethlehem and descended from David, but they contradict each other. Since Jesus lived about 1000 years after David, it’s likely that a lot of people around then were his descendants and wouldn’t have known it.
That said, most of Jesus’ teachings that we know of do relate to messianic ideas of the time. He taught of a coming age when things would be ideal, and that his followers should act as if it’s already arrived. Even the resurrection was tied in with a common Jewish eschatological idea of the time, that the dead would physically come back to life in the end times.
Jesus would, therefore, have been the harbinger of the general resurrection. The main problem with Jesus being Messiah is that the Messianic Age didn’t arrive. It wasn’t too long before Christian teaching became that Jesus would bring this about during his Second Coming, which as far as we know still hasn’t arrived. So we’re left with a Messiah in the past, but the Messianic Age still in an unspecified future time.
Christian Zionists seem to think the Second Coming will lead to a great number of Jews deciding Jesus was the Messiah after all.
Jewish belief is that the Messiah hasn’t arrived yet, but how important this is varies somewhat, and it’s really confusing that people who call themselves Messianic Jews are actually Christians. I understand that Reform Judaism doesn’t necessarily teach that there will be an individual Messiah, but the Messianic Age will still be a thing. From what I’ve read, believers in a coming Messiah think he will likely either show himself at the time of greatest need, or when the people’s behavior most merits it, kind of total opposites. There’s also a teaching in the Talmud and other sources that the Messiah would have to arrive by the year 6000, which would be in 2239 through 2240 on the Gregorian Calendar. How common this belief still is, I couldn’t say.