According to some later legends, Erebus was part of Hades, the underworld. It was where the dead had to pass immdiately after dying. After Charon ferried them across the river Acheron, they entered Tartarus, the underworld proper.
Erebus was often used as a synonym for Hades, the god.
Mount Erebus is an Antarctic volcano.
Aristophanes, Birds; Hesiod, Theogony.