Final answer:
The Greeks established colonies primarily during the Archaic period due to land shortages, founding settlements across the Mediterranean and Black Sea regions. These colonies, located near the sea, became independent city-states and played key roles in Greek trade and cultural expansion.
Step-by-step explanation:
The Greeks primarily established their colonies during two main periods: the Archaic period and the subsequent period leading up to the Roman domination. During the Archaic period, which lasted from 600 to 480 BCE, Greeks colonized various regions due to a shortage of farmland at home. They established colonies in resource-rich areas along the shores of the Black Sea, the northern Aegean, North Africa at Cyrene in Libya, southern Gaul at Massalia (modern Marseille), and notably in southern Italy and on the island of Sicily, in a region they called Magna Graecia or 'Greater Greece'. These colonies became independent polis with their own laws and systems of governance, emphasizing the ideals of citizenship, equality, and participation. Colonization also expanded to coastal Spain and France, as well as to Egypt and Persia via trading posts.
Colonies were typically located near the sea, ensuring connectivity with the Greek world through maritime trade. It was also during this time that Athens developed democracy and along with other city-states like Sparta, Corinth, and Thebes, played central roles in regional politics. Following the Archaic period, Greek colonization continued to influence and shape the Mediterranean world, as it became a part of their larger cultural and economic network — a precursor to the eventual unification under the Roman Empire.