In Greek mythology, Tartarus is both a deity and a place in the underworld. In ancient Orphic sources and in the mystery schools, Tartarus is also the unbounded first-existing entity from which the Light and the cosmos are born.
In the Greek poet Hesiod's Theogony, c. 700 BC, Tartarus was the third of the primordial deities, following after Chaos and Gaia (Earth), and preceding Eros, and was the father, by Gaia, of the monster Typhon. According to Hyginus, Tartarus was the offspring of Aether and Gaia.
As for the place, Hesiod asserts that a bronze anvil falling from heaven would fall nine days before it reached the earth. The anvil would take nine more days to fall from earth to Tartarus. In the Iliad (c. 700 BC), Zeus asserts that Tartarus is "as far beneath Hades as heaven is above earth."
(ref.: https://en.wikipedia.org/wiki/Tartarus)