Messiah

In Christianity, Jesus is the Messiah, who is supposed to deliver the world from sin. Jewish scholars use the term "Moshiach" instead of "Messiah," to differentiate from the Christian idea of a divine savior. The Torah does not actually mention the idea of a Moshiach directly--his coming was predicted later by prophets like Isaiah and Jeremiah. These prophecies say that the Moshiach is destined to bring all the Jews back to Israel, where they will restore the land to its former glory and rule the world from Jerusalem. The Moshiach will be a great political and military leader who will observe all the laws of Judaism and usher in a utopian age for the world. Everyone everywhere will worship the Jewish God, and there will be no war, famine, disease, sin, or anything else bad.

Judaism puts few restrictions on who the Moshiach might be; basically, anyone who succeeds in doing what the Moshiach is prophesized to do is deemed to be the Moshiach. Some scholars debate the specific date or conditions under which he will appear, while others think it is foolish to try to predict this because a wrong guess would result in disillusioned Jews. Many people throughout history have claimed to be the Moshiach, such as Shimeon ben Kosiba, Shabbatai Tzvi, and the slightly-more-famous Jesus, but they were rejected on the basis of failure to produce an everlasting golden age for the world.

http://www.jewfaq.org/moshiach.htm contains this information and more.