SELinux stands for Security Enhanced Linux, it and is a Linux kernel security model, created by the National Security Agency (NSA), that provides a hardened set of access control security policies for the Linux operating system. Specifically, SELinux is an implementation of Mandatory Access Controls (MAC), which is a type of access control that constraints the ability of either a subject or initiator to access or act upon an object.
The SELinux kernel module has been added to a number of Linux distributions, such as Red Hat Enterprise Linux, CentOS Stream, Fedora, and even Android.
SELinux tends to get a bad rap, because it often seems to go out of its way to prevent legitimate applications from working. This article from TechRepublic Premium intends to change that since fundamentally, SELinux is pretty simple to understand.
In the article: