Ghost

A ghost is a character's representation upon death while playing in Hardcore mode. Ghosts can continue to explore the world, fly limitlessly, and pass through blocks. They cannot be seen by other players and cannot be harmed, nor can they attack, or interact with the world in any way; though they can continue to chat with other players in multiplayer.

When a player dies and becomes a ghost, all their items are dropped at the location of their death. If they log out, their character is permanently deleted. The .plr file can be restored from the system trashcan to the Players folder thus restoring your character to the pre-death state.