Philosophy of law is a way of thinking about the law (like a set of rules for people to follow to stay safe and get along with each other). It's a way of understanding what laws really mean, why they exist, and when it's okay or not okay to break them. It's like asking why we have rules at home and at school - to help keep us safe, so that we can learn, and so that we can all get along. Philosophy of law is also a way of figuring out whether laws are fair or unfair, and when it should be changed or not. So basically, it's like a way of thinking about the law to help us make better and fairer decisions about it.