This existence is in a shadowy spectral body form in a place called sheol which, on some accounts, was in a vast cavern beneath the surface of the earth. This is the worldview backdrop against which we should read the story of the Witch of Endor calling up the ghost of Samuel (1 Samuel 28).
Note how this background worldview and the details of the story both fit comfortably within the contemporary concept of ghosts as people who have survived the demise of their physical bodies and continue to exist with a spectral body.
This basic picture was shared by the ancient Greeks and Romans and can be seen operative in the background worldview of the disciples of Jesus.
Consider Mark 6:48-50:
He was about to pass by them, but when they saw him walking on the lake, they thought he was a ghost. They cried out, because they all saw him and were terrified.
Since ghosts were a part of the background worldview of the disciples it is understandable that when they first saw Jesus they thought he was a ghost.
A rich understanding of the world of ghosts is also behind Luke 24:36-37:
While they were still talking about this, Jesus himself stood among them and said to them, "Peace be with you." They were startled and frightened, thinking they saw a ghost.
At this point Luke shows a real awareness of the popular first century views on ghosts among Greeks, Romans and Hebrews for he carefully distinguishes the post-resurrection body of Jesus from disembodied spirits, revanants (that is, mere reanimated corpses), immortal heroes and translated mortals (see Deborah Thompson Prince, "The 'Ghost' of Jesus: Luke 24 in Light of Ancient Narratives of Post-Morten Apparitions", JSNT, 29, 3 (2007), 287-301). This is the rich world of ghosts that frames the "pareschatology" of the Bible.
Source: christianpost.com