@
nerv234
https://wow.gamepedia.com/Ghost, do read up on it but I'll provide these details here as one of the subsection entry:
"The term "ghost" is sometimes applied to any undead incorporeal being"
Ghostly beings
Banshee
Shade
Spectre
Troll spectre
Spirit Healer
Val'kyr
Wisp
Wraith
Spirit beast
Spectral gryphon
Spectral saber
Spirit wolf
Here's what it means to be undead:
"The undead are beings that have died and have had their souls trapped between life and death. They derive power from necromantic magic.[1] Most common examples being zombies or ghosts, undead are typically mindless, bloodthirsty fiends hostile toward any living thing that comes across their path. But some have managed to retain their memories and be who they were in life."
The list of Incorporeal Undead:
Incorporeal
Incorporeal undead are ghosts and spirits of the dead.
IconSmall Banshee.gif Banshee
IconSmall Ghost.gifIconSmall GhostCaptain.gifIconSmall GhostMogu.gif Ghost
IconSmall Ghost.gif Phantom
IconSmall SpectralGryphon.gif Spectral gryphon
IconSmall RevenantDeath.gif Revenant
IconSmall Shade.gif Shade
IconSmall Spectre.gif Spectre
IconSmall Val'kyr.gif Val'kyr
IconSmall SpiritHealer.gif Spirit healer
IconSmall Wisp.gif Wisp
IconSmall Wraith.gif Wraith
Your gamepedia Banshee entry:
"Banshees are incorporeal undead elf women, known for their unholy screams and the unsettling ability to possess the bodies of their enemies. Highborne and night elf banshees have existed since the time of the War of the Ancients,[1] but many were also created when the Scourge invaded Quel'Thalas and slaughtered the majority of the kingdom's high elf inhabitants during the Third War. Many banshees now serve the ruler of the Forsaken, the "Banshee Queen" Sylvanas Windrunner."