Short answers, pulled from the story.
Ancient Greece was a northeastern Mediterranean civilization made up of a loose collection of culturally and linguistically related city-states. It existed from the Greek Dark Ages of the 12th to 9th centuries BC to the end of classical antiquity, around 600 AD.
Classical Greece is considered the cradle of Western civilization because its culture, especially philosophy, shaped ancient Rome, which spread a version of it across the Mediterranean and Europe. The modern West derives many of its founding ideas in politics, philosophy, science, and art from it.
Before the Roman period, most Greek regions were officially unified only once, under the Kingdom of Macedon from 338 to 323 BC. Philip II compelled most poleis to join his Corinthian League rather than annexing their territory.
Athens founded the world's first democracy after ending its tyranny in the second half of the 6th century BC. A citizens' assembly called the Ecclesia had existed since Draco's reforms in 621 BC, and Cleisthenes carried out further democratising reforms after Hippias was overthrown.
By 600 BC chattel slavery had spread in Greece, and by the 5th century BC slaves made up one-third of the population in some city-states, with between 40 and 80 percent of Classical Athens enslaved. Sparta had a special class called helots, Messenians enslaved en masse during the Messenian Wars.
Ancient Greek scholars developed geometry, formal mathematical proof, and advanced astronomy, with Aristarchus of Samos first suggesting a heliocentric system in the 3rd century BC and Eratosthenes estimating the Earth's circumference. The Antikythera mechanism, dating from about 80 BC, was the first ancestor of the astronomical computer.