Security-enhanced Linux is a feature of the Linux(R) kernel and a
number of utilities with enhanced security functionality designed to
add mandatory access controls to Linux. The Security-enhanced Linux
kernel contains new architectural components originally developed to
improve the security of the Flask operating system. These architectural
components provide general support for the enforcement of many kinds of
mandatory access control policies, including those based on the
concepts of Type Enforcement(R), Role-based Access Control, and
Multi-level Security.

libselinux provides an API for SELinux applications to get and set
process and file security contexts and to obtain security policy
decisions. Required for any applications that use the SELinux API.