Over two thousand five hundred years ago, ancient Greece was actually made up of many hundreds of Greek city-states, grouped together.
The ancient Greeks believed in thousands of gods, goddesses, and magical creatures. They built temples to honour their gods. Honouring their gods was part of their daily life and part of just about everything they did. That's because they believed their gods controlled the heavens and earth, and could interact with humans and cause all kinds of trouble.
A huge mountain range ran down the middle of the Greek peninsula. The people believed that the ancient Greek mystical world was ruled by a small group of powerful gods called the 12 Olympians, who lived at the top of the highest mountain, Mount Olympus.
The Greeks told wonderful myths about their gods. Poseidon, lord of the sea, could raise his hand and a new island would appear! Apollo brought up the sun every day, and his twin sister Artemis brought up the moon. Most of the gods avoided Ares. Nobody liked him much, but he was the god of war, so you had to keep him on your side if you could.
The mighty Zeus, king of all the gods, probably caused more trouble than any of them, even more than Aphrodite, the goddess of love. The Greeks did not limit their myths to stories about the 12 Olympians. They told stories about nearly all the magical, mythical creatures in which they believed.
Many of their mythical beings looked like people, but some looked like monsters, because, well .. they were monsters! Fortunately, the ancient Greeks found a way to beat monsters, nearly always with trickery and cleverness, two skills that were greatly admired by the ancient Greeks.
Ancient Greece was not a country. It was not an empire. It was a collection of over 1500 independent city-states, each with its own government and its own way of doing things. Some city-states, like ancient Corinth, were ruled by kings. Some, like the warrior city-state of Sparta, were ruled by council. Ancient Athens, the jewel of the ancient Greek city-states, experimented with an early form of democracy. The ancient Greeks were very loyal to their city-state.
The Greek city-states did, on occasion, team up against a common foe. They also went to war with each other (quite often), unless the Olympic Games were in progress. The Greeks invented the Olympics, and took the event very seriously. Nearly all the ancient Greek city-states sent teams to participate. If two or more Greek city-states happened to be at war with each other when the games were on, the war was halted for the duration of the games. The Greek Olympics were not the only games in ancient Greece - the Greeks loved competition of all sorts - but the Olympics were the most important.