Anagnorisis is a big, fancy word that means "discovering something important."
Imagine you are playing hide-and-seek with your friends, and you find a really good hiding spot. You are convinced that no one will be able to find you there.
But then, one of your friends accidentally bumps into something and makes a loud noise. Suddenly, you realize that your hiding spot is not so secret after all. You have had an anagnorisis - you have discovered that your hiding spot is not as good as you thought it was.
People use the word anagnorisis to talk about moments in stories where the characters realize something really important. For example, in the story of Cinderella, the prince realizes that Cinderella is the girl he has been looking for all along. This is an anagnorisis moment for him.
So, anagnorisis is like a lightbulb moment when you figure out something really important that you didn't know before.