Tartarus is a horrible place, and coincidentally the Titans and Giants got banished there by Zeus, due to spying and raiding Mount Olympus before the next war.Tartarus is also an ancient God who is married to Gaia. He sired the giants.
Purpose[]
It is used for a 'dungeon of torment,' but the Titans and Giants are living normally because they are used to it. Since some Titans or Titanesses can fly, they can escape Tartarus and do their duties, but Zeus most probably is watching over them, so they probably return each night if they have night duties.