Okay, so imagine there is a big rule book called the "Goodness Book" and it tells us all the things we should do to be good people. It says things like "Be kind to others" and "don't hurt anyone."
But some people decide they don't want to follow the Goodness Book. They might be mean to others and do things that hurt people, like stealing or saying mean things. This is called wickedness.
When someone is wicked, they are being very bad and not following the rules in the Goodness Book. It's important to try to be good and follow the rules, because that's how we all get along and make the world a happier place.