Online security involves protecting systems and data while connected to networks, using tools like firewalls, antivirus software, secure VPNs, and strong passwords to prevent cyberattacks. Offline security focuses on physical safety, protecting documents and devices from unauthorized access, theft, or damage through methods like secure storage, physical access controls, and regular device updates. Both are essential and often work together; for example, offline data backups protect against online attacks, while online access control can monitor physical access.