Short answers, pulled from the story.
Hesiod describes five distinct ages: the Golden Age, Silver Age, Heroic Age, Bronze Age, and Iron Age. The first age was ruled by Cronus with peace and abundance, while the second followed under Zeus with strife among men.
Ovid omits the Heroic Age entirely and describes only four ages instead of five. He states that innocence and justice defined his Golden Age while truth and loyalty disappeared completely during the Iron Age.
Saint Jerome placed the Golden Age from 1710 BC to 1674 BC and the Silver Age from 1674 BC to 1628 BC. His chronology dates to the fourth century AD and attempts to align mythology with recorded history.
Zeus destroyed the Silver Age because these men refused to worship the gods after living for one hundred years under their mothers' dominion. They spent only a short time as grown adults before strife led to their destruction.
Hesiod uses gold, silver, bronze, and iron to symbolize decreasing value yet increasing hardness across the ages. Gold represents peace, silver marks maternal rule, bronze signifies war, and iron symbolizes toil and social breakdown.