What is SELinux? SELinux is a set of security policies/modules which are going to apply on the machine to improve the overall security of the machine.
These are the Linux security modules(LSM) which are loaded in to kernel to improve security on accessing services/files which improve security. SELinux is short form of Security Enhanced Linux. SElinux is a security feature which was shipped with RHEL5, it is much secure than any other security such as PAM and Initd. Apparmor is some times consider as eloquent to SELinux. Below is the security model in Linux.