Short answers, pulled from the story.
The Golden Age is the first and best of five ages described by the Greek poet Hesiod in his Works and Days. During it, the Golden Race of humanity lived without toil, sorrow, or old age; the earth provided food freely; and when people died, they passed peacefully as though overcome by sleep, with their spirits living on as guardians.
In classical Greek mythology the Golden Age was presided over by the Titan Cronus; in Latin literature the equivalent role belonged to the god Saturn. Some versions also include the goddess Astraea, who lived among humans through the Silver Age before fleeing to become the constellation Virgo when men turned violent in the Bronze Age.
Hesiod says the Golden Age ended when the Titan Prometheus gave humanity fire and the arts of civilization. Zeus punished Prometheus by chaining him to a rock in the Caucasus and sending Pandora to Prometheus's brother Epimetheus. When Pandora opened the forbidden box entrusted to her, every form of evil entered the world.
The Hindu equivalent is Satya Yuga, the first of four yugas in the cyclical Yuga Cycle. According to the Mahabharata, during Satya Yuga men neither bought nor sold, disease did not exist, and all that was required could be obtained by the power of will. Hindu teaching holds that we are currently in Kali Yuga, the dark age.
Writing roughly between 44 and 38 BCE, Virgil introduced political allegory into the pastoral tradition, suggesting in his fourth Eclogue that a new Golden Age of peace and justice was about to return. He later composed the Georgics in 29 BCE, modeled on Hesiod's Works and Days, as an allegory linking man's alteration of nature to good and bad government.
A Greek literary tradition identified Arcadia, an impoverished rural region where herdsmen ate acorns and the god Pan dwelt on Mount Maenalus, as the site of the original Golden Age. The poet Theocritus in the 3rd century BCE and then Virgil cemented it as an idealized pastoral landscape, representing what art historian Erwin Panofsky called a dream of perfect bliss surrounded with a halo of sweetly sad melancholy.