Persephone (Proserpine to the Romans) was the beautiful daughter of Zeus, king of the gods, and Demeter, goddess of agriculture. Persephone also goes by the name of Kore or Cora, and she is thought of as the maiden goddess of spring and grain. In the most popular myth of Persephone, she's the unwilling wife of Hades, lord of the underworld, and must spend a few months out of the year with him in the land of the dead. Nothing grows on earth when Persephone is among the dead, because Demeter is so sad about her daughter's fate. And so the myth of Persephone is used to explain the seasons.
Interestingly, in earlier myths Persephone is depicted as the perfectly willing queen of the dead who rules the underworld beside her husband, Hades. In these myths, she wasn't depicted as an innocent maiden at all, but the stone-cold goddess of the dead. In The Odyssey, for example, Homer calls her the majestic queen of shades. This earlier version of Persephone was often called Despoina, which translates to "the mistress." People called her this because they were afraid to say her real name.
Eventually, it seems Persephone's two personas blended together, and so she was thought of as a goddess of both life and death. Whatever the case, Persephone is almost always associated with the death and resurrection of the earth through the cycle of the seasons. She and Demeter were the central figures in Eleusinian Mysteries, a cult practice which promised its initiates everlasting life. (See "Context" for more on the Eleusinian Mysteries.)