Case law is like a teacher's rule book that helps judges decide how to handle different situations in court. Let's pretend the teacher is the law and the rule book is the case law.
So, when someone goes to court and presents a problem, the judge looks in the rule book (case law) to see what other judges did in similar situations. It's kind of like asking other teachers how they taught a lesson in the past.
The judge then decides what to do based on what the rule book says and what they think is the best solution for the problem. Just like how a teacher decides on how to teach a new lesson based on what they've learned from other teachers and their own experience.
Case law is very important because it helps judges make fair decisions that are based on past experiences and it also helps make the law more consistent.