Earth Mother, goddess of agriculture, grain.
The story is told that Demeter and her daughter Persephone are separated when Persephone is captured and raped by Hades.
Demeter is grief stricken and wonders the earth unable to create the life-giving grain. The story explains the seasonal changes, and may well also deal with the changing of their society to patriarch based.
Demeter is a double or perhaps triple goddess (maid, mother) or (maid, mother, crone). In her double persona she is both Demeter (mother) and Persephone (maid), in the triple she is Demeter, Persephone and Hecate (crone).
Her name, Demeter (Ceres for the Romans), literally means grain mother or mother earth.