ELI5: Explain Like I'm 5

Vengeful ghost

A vengeful ghost is a ghost (a spirit of a person that has died) that is very angry and wants to hurt or scare people. People who believe in vengeful ghosts think that if something bad happened to someone when they were alive (like if someone was treated unfairly or abused) then the spirit of that person could come back after they die to try to scare or punish the people who hurt them.