According to NIST Special Publication 800-53, Revision 4:
[It] provides a catalog of security and privacy controls for federal information systems and organizations and a process for selecting controls to protect organizational operations … , organizational assets, individuals, other organizations, and the Nation from a diverse set of threats ….
The controls are customizable and implemented as part of an organization-wide process that manages information security and privacy risk. The controls address a diverse set of security and privacy requirements across the federal government and critical infrastructure, derived from legislation, Executive Orders, policies, directives, regulations, standards, and/or mission/business needs.
The [NIST 800-53, Revision 4] publication also describes how to develop specialized sets of controls, or overlays, tailored for specific types of missions/business functions, technologies, or environments of operation.
Finally, the catalog of security controls addresses security from both a functionality perspective (the strength of security functions and mechanisms provided) and an assurance perspective (the measures of confidence in the implemented security capability). Addressing both security functionality and security assurance ensures that information technology products and the information systems built from those products using sound systems and security engineering principles are sufficiently trustworthy.