The Netherworld of the Force, also known as the Mist-Beyond, the afterlife, or the Garden Beyond, was the place the souls of every being and creature were thought to ascend to after their physical bodies died. The Jedi Master Qui-Gon Jinn went to this realm after he was killed by Darth Maul, but, thanks to the help of the Force Priestesses, he managed to return to the physical universe as a Force spirit.
Chaos was an unpleasant mythical place and was different to the Netherworld.
The Netherworld of the Force was first mentioned in the 2005 film Star Wars: Episode III Revenge of the Sith, the third and final installment of the Star Wars prequel trilogy. However, the Netherworld had been first conceived by George Lucas as early as the revised rough draft of the 1983 film Star Wars: Episode VI Return of the Jedi.