The protection of computer systems and information from threats such as theft or data destruction.
The security tag is used in the context of computer security.
Computer Security is a very broad term:
The objective of computer security includes protection of information and property from theft, corruption, or natural disaster, while allowing the information and property to remain accessible and productive to its intended users.
Questions on Super User tagged security are generally expected to relate to specific software or hardware problems associated with security considerations.
Questions about protecting information assets from threats through controls, security architecture and security management systems are generally better suited for Security.StackExchange.