How did Ancient Greek religion work?

In the most famous Greek religious book, The Iliad, the gods directly interacted with people.

They had the same feelings and could be jealous, angry, selfish, and fall in love, and many were thought to live at a real place in Greece: Mount Olympus in the north. 

Because of this, the main Greek gods were called the 'Olympians'. The king of the deities was Zeus, and he had power over the sky, storm and lightning. 

The main religious buildings in Greek religion were temples. They were not like today's churches: ordinary people usually could not go inside to worship them.

Instead, the temples were the homes of them where they lived, and only the priests could see them regularly. 

Usually, the more important a god was to a city-state, the more impressive their temple was; for example, Athena, the lead goddess of Athens, had the largest and most costly temple.

It stood on the highest hill in the city. If a person wanted help from a god, they would go outside the temple to pray and leave a gift, in the hope the god would answer. 

Sometimes, everyone in a city took part in a large religious ceremony. During these ceremonies, it was common for animals to be offered and the meat might be cooked and shared with the worshippers.

In Greek religion, gods were among the super-powered beings; the Greeks also believed in a group called the 'demi-gods' or 'heroes'.

A demi-god was someone whose one parent was a deity and the other was a human.

As a result, a demi-god had some of the powers of their divine parent, but also some of the weaknesses of their human parent. 

Still, their powers let them perform great and brave deeds, which is why they were called 'heroes'.

Some famous Greek heroes were Heracles, who had great strength, and Achilles, who could not be killed in battle. 

The ancient Greeks believed people lived on after death. They thought there was a place below the ground called 'Hades', or, in other words, the underworld. A god, also named Hades, ruled it. 

Hades was seen as a real place that someone could, in theory, reach while they were alive, but it was separated from the living world by the River Styx, which could only be crossed after death.

To move souls across the river, a boatman named Charon was responsible for transporting them in exchange for a small payment. 

For that reason, Greeks put coins with the body at funerals. 

Once in the underworld, a dead person faced a judgment to decide where in that realm they would spend eternity.

If they had done good deeds in life, they went to a place of peace called the Elysian Fields, but if they had been evil, they went to Tartarus, where they were punished forever.