What is "thesmophoria"

Thesmophoria was a festival held in Greek cities, in honor of the goddesses Demeter and her daughter Persephone. The name derives from thesmoi, or laws by which men must work the land. The Thesmophoria were the most widespread festivals and the main expression of the cult of Demeter, aside from the Eleusinian Mysteries. The Thesmophoria commemorated the third of the year when Demeter abstained from her role of goddess of the harvest and growth; spending the harsh summer months of Greece, when vegetation dies and lacks rain, in mourning for her daughter who was in the realm of the Underworld. Their distinctive feature was the sacrifice of pigs.