Cyber security refers to the practice of protecting computer systems, networks, and data from unauthorized access, damage, or theft. This lesson covers the broad scope of cyber security — spanning personal device protection, business network security, and large-scale organizational defense — and why it has become increasingly critical as more of our personal and professional lives move online. It also introduces the idea that cyber security is not just a technical field but involves policies, awareness, and human behavior just as much as tools and technology.