Okay, so lilitu is a word that comes from ancient Mesopotamia, which is an area in the Middle East where people lived a really long time ago - like, thousands and thousands of years ago.
Lilitu is actually the name of a type of female demon that was believed to be harmful and wicked. People who lived in Mesopotamia a long time ago were really superstitious and believed in all sorts of weird creatures and demons.
So basically, lilitu was one of those creatures that people were afraid of because they thought it could cause them harm or even possession. But don't worry, because the idea of lilitu and these other demons is just a thing of the past and nobody believes in them anymore.