GNU/Linux

Linux or GNU/Linux is a Unix-like operating system (or family of) for computers.

The Linux kernel (the basis of the operating system) is free software, meaning everyone has the freedom to use it, see how it works, change it, or share it.

There is a lot of software for Linux and—like Linux itself—a lot of the software for Linux is free software. This is one reason why many people like to use Linux.
— Simple English Wikipedia

Personally I use Linux with NixOS distributions.

One of Unix/Linux important idea is everything is a file, with some exceptions (semaphores, processes and threads).

Linux features

• SYSRQ key
• X11 forwarding
• Linux kernel features - Wikipedia

External links

• Linux Inside
• Learn Enough Command Line to Be Dangerous | Learn Enough to Be Dangerous
• Top 40 Linux Commands for All Users + Free Linux Cheat Sheet
• The 50 Most Popular Linux & Terminal Commands - Full Course for Beginners - YouTube