Myths tell the stories of ancestors and the origin of humans and the world, the gods, supernatural beings (satyrs, nymphs, mermaids) and heroes with super-human, usually god-given, powers (as in the case of Heracles or Perseus of the Greeks). Myths also describe origins or nuances of long-held customs or explain natural events such as the sunrise and sunset, the full moon or thunder and lightning storms.
Persephone, Heraklion Archaeological Museum, Crete
One of the most famous myths of ancient Greece is of Demeter, goddess of the grain, and her daughter Persephone. Persephone was kidnapped by Hades and brought down to the underworld. Demeter searched desperately everywhere for the maiden but could not find her. During this time of Demeter’s sorrow the crops failed and people starved and the gods were not given their due. Zeus, king of the gods, ordered Hades to restore Persephone to her mother and Hades obliged but, because Persephone had eaten a certain number of pomegranate seeds while in the underworld, she had to spend half the year below the earth and could enjoy the other half with her mother.
This story explained the change of the seasons in Greece. When it is warm and the fields are bountiful, Persephone is with her mother and Demeter is happy and causes the world to bloom; in the cold and rainy season, when Persephone is below the earth with Hades, Demeter mourns and the land lies barren.
sourse: http://www.ancient.eu/mythology/