The Ramchal, in part 1 of Maamar HaGeulah, writes that 4 things occur during Galus, each with its own benefit. All 4 are to be repaired during the Geulah.
- Hastarat Panim - The "pipes" through which abundance arrives at Am Yisrael from Heaven are "clogged", so to speak, only allowing what is necessary to pass through. It is lack of strength and abundance, and also the Torah and Wisdom is lacking.
- Great Abundance for the Nations of the World - From an expression in Pesachim 42:2 - If this one is full, this one is desolate.
- Galus of the Shechinah - Because the Shechinah is in exile, this strengthens the effects of the abundance given to the nations.
- The Sufferings of Galus (and their benefit) - The Ramchal here writes that the benefit of this suffering is to (to quote Daniel 9:24) to finish transgression and end sin. That is to say to serve as atonement for Am Yisrael's sins.
He then goes on to say that the Geulah itself is divided in to two parts, the Pekidah and the Zechirah. These two ideas will require their own posts.