What is Reformed Theology/Calvinism 8: God's "desire" or will to save everyone?

What does the Bible mean when it tells us God desires or wants all to be saved? Who are the "all"? What is the difference between the prescriptive will of God & the sovereign will of God? Does God have "wants" or unmet desires like a man? What is anthropopathism & anthropomorphism? If God doesn't save all men like some say He wants to, then does He mourn for all eternity over the fact that they are lost?