Cyber refers to the digital domain where networks, systems, data, and online services are protected, observed, or targeted. It includes everything that depends on connected computers: servers, cloud platforms, industrial control systems, mobile devices, and the communications links between them.
In cyber security, the term matters because attackers can reach critical operations without crossing a physical border. Common threats include phishing, malware, ransomware, credential theft, and denial-of-service attacks. Defenders use monitoring, logging, patching, access control, segmentation, backups, and incident response to reduce risk and limit damage. In defense and government settings, cyber is treated as a core operational domain because disruption of digital infrastructure can affect command, logistics, intelligence, and public services. Strong cyber capability is therefore not just about preventing hacks; it is about maintaining resilience, continuity, and control when systems are under pressure.