SELinux stands for Security-Enhanced Linux. Because Linux is built by collection of open source, it causes security problems. Unlike Window, software is build by trusted professionals. In Linux, the source code is written by some unknown people who may be hackers or criminals, so a system administrator must restrict what a open source software can do. Unlike Different from Window, software is written by expert. In Linux, most open source is written amateurs or students, so it may contains serious bugs that will damage your system. The system must be protect by SElinux.