What exactly will Moshiach do ?
Based on numerous verses in the scriptures, here are some of the changes that Moshiach will affect. He will redeem the Jews from the exile and oppression that we are now undergoing, and bring us all to Eretz Yisroel. He will rebuild the Holy Temple, and reinstitute the sacrifices. He will reinstate a form of government according to the way the Torah dictates. Namely, a king from the seed of David, the Sanhedrin, and all the laws will be based on the mitzvos of the torah and not on secular ideas and culture. The Messiah will bring an end to all wars, and the evil will be punished for their sins, and the righteous will be rewarded for their good deeds, each person according to his actions. However the most important and encompassing factor about Moshiach will be that we will merit to having the Divine presence among us. This will cause the whole world to realize the Hashem is the supreme ruler and creator of the world, every nation will want to get close to Hashem at that point. At that point the will of all humanity will be solely to gain closeness to the divine presence and to achieve closeness to Hashem. Additionally, because the Divine presence will be readily noticeable, the world will have a tremendous bounty, even in a physical sense. The animal will not even fight with each other, and there will be a tremendous amount of physical pleasures and bounty.
We pray numerous times daily that this time should come soon.