Who is she?
Demeter is the goddess of the harvest and agriculture. She is also recognized as the goddess of health, birth and marriage. Her roman counterpart is Ceres and is the daughter of Kronos and Rhea and mother of Plutus, the god of wealth and soil,(Encyclopedia Britannica). She is the sister of Zeus, Hera, Poseidon and Hades. Her daughter is Persephone, the goddess of spring growth, (Michael Stapleton).
How do Greeks recognize her?
Demeter has no less than six different festivals that celebrate her existence, (Encyclopedia Britannica). One of those is Thesmophoria, a fertility festival that was attended by only women in Athens, (Columbia Encyclopedia). Her sacred items are fruits and the torch- she used the torch when searching for Persephone in the underworld. Demeter is represented by the snake and the pig, (Lindemans).
Demeter's daughter Persephone was stolen by Hades and he made her the queen of the underworld. A world wide famine occurred when Demeter went in search of her daughter because her attention was diverted from maintaining agriculture growth. Growth didn't pick up until Zeus ordered Hades to return Persephone. But Hades gave her a pomegranate which forced her to spend two-thirds of the year in the underworld. (Encyclopedia Mythica).
How has she effected humans?
Food only grows in the late Spring/ early Summer because that is the time when Persephone is allowed to stay with her mother. She created a famine when she went to the underworld to find Persephone. She is also credited with ending human nomadic life by teaching them how to plant crops and farm, (Encyclopedia Mythica).