In myth, Demeter was believed to have stayed in Eleusis while she was mourning the loss of her daughter Persephone. She handed the secrets of agriculture and fertility to the king's son, Triptolemos. Each year people from all around the Greek world came to learn these secrets at a festival in Eleusis called the the Eleusinian Mysteries.
We know very little about what happened at this festival. People who had taken part in the Mysteries had to keep their experiences a secret. Therefore we have hardly any written material on the events that took place at Eleusis.