Ghosts are dead humans that didn't do very bad deeds, or died when they were born. They also were not buried 24 hours after death.
Ghosts look almost exactly like their human form, but they are a tiny bit transparent, but it isn't that noticable. If a human died when they are 3 or younger, they age as a ghost until around the hypothetical age of 18, but they are still immortal.
Ghosts can't die unless if they get in contact with iron for too long, or if their soul is crushed.
Ghosts normally are very silly and carefree, and like to mess with people, play pranks, and play around. Though all Ghosts aren't always like that, thats what they are normally seen as.
Ghosts started existing when the first humans passed away. Humans never buried the deceased, so all deceased became Ghosts. Only a few 100 years later when all people started burying the deceased, Ghosts became less common, and they only have recently descovered them.
All Known Ghosts