What is Knowledge Representation?
How would you describe all the knowledge in the world, and what would you do with it? That, in a nutshell, is the concern of Knowledge Representation, a sub-field of study within Artificial Intelligence. It's a process that takes all the concepts in a domain, establishes how these concepts relate to each other, and defines the rules that control how they behave.
To illustrate, think about the real world. It's large and infinitely complex. So we can reduce it to an abstract model — for instance, a map that captures only aspects of the world that are relevant to us, such as its geography. But the computer can't understand a map, so we reduce this even further into a set of rules and statements that represents the map. In other words, KR represents information in a way that computers can understand.