Demeter is the goddess of agriculture and the seasons. That last one was because of Hades; he had eloped her daughter Persephone, and when Demeter forced him to free her, she had already eaten a peach. And everyone who eates something in the underworld, is never leaving it again. But when Demeter asked Zeus to help, she and Hades got to a compromise, Persephone would be half a year in the underworld with Hades and half a year on the Olympus with Demeter. In the time Persephone was with her mother, Demeter was happy and it was spring and summer, but when her daughter was in the underworld and Demeter was so sad that no plants would grow; this became the autumn and winter.