Bots are stupid. All they know to do is point at the nearest target and shoot, or run for the nearest pickup that's in sight. They're great at getting to things they can see. But how do they get from room to room? If their health is low, how do they find their way to a health pickup? Well, Unreal generates a path network that connects everything in your level. That way, if a bot has no one to shoot, or is low on health, they know how to run through hallways to different rooms where there are goodies for them to pick up.