Kids IT Lab No.1 | Linux

What Is Linux? A Beginner's Guide

Android on your phone. Over half of all websites on the internet. Every single one of the world's top 500 supercomputers. All of them run on an OS called "Linux." Linux is free, open to everyone, and continuously developed by engineers around the world. This article explains what Linux is, where it runs, and how you can try it — with diagrams to help.

So, what exactly is Linux?

Linux is a type of "OS (Operating System)" — the basic software that runs a computer or smartphone. It belongs to the same family as Windows and macOS. The difference comes down to two things: first, it's free; second, the source code is publicly available, so anyone can modify it.

In 1991, a Finnish university student named Linus Torvalds started it as a hobby project and invited the internet to help improve it. More than 30 years later, engineers around the world have been adding their touch little by little, turning it into the massive system it is today.

"Free" doesn't mean "cut-down." Linux is actually the serious standard environment used in servers, cloud computing, and research computers. It looks different from Windows or Mac, but it performs the same OS duties: managing files, running apps, and connecting to networks.

How it works: kernel and distributions

Strictly speaking, "Linux" refers only to the core of the OS (the kernel). When you actually use it, you install a "distribution" — a bundled package that combines the kernel with tools and apps. Popular ones include Ubuntu, Debian, Fedora, and Arch Linux; you pick the one that fits your needs.

Linux's 4-Layer Structure (built from the bottom up) The kernel is the foundation. Tools, a GUI, and apps stack on top to create a usable system. ④ Application Layer Firefox / Chrome / VS Code / LibreOffice / Steam (what users directly touch) ③ Desktop Environment GNOME / KDE / XFCE (handles the visual "look and feel," like Windows does) ② System Tools (GNU + Shell) Bash, grep, cat, and hundreds of other commands. Together with the kernel, this is "the Linux system." ① Linux Kernel (OS core) Talks to hardware · 30 million lines of C · released 1991 (by Linus Torvalds) ①+② packaged together = a "distribution" (Ubuntu, Debian, Fedora, etc.)
Fig. 1: Linux is built in 4 layers. What's called "Linux" is technically just layer ①; distributions include up to layer ②.

Where does Linux run?

Linux is the "unsung hero" that supports the world from places you don't see. Most of the services you use every day run on Linux on the server side.

Where Linux Runs (market share) Sources: TOP500, W3Techs, StatCounter (2025 estimates). Metrics differ by field. Supercomputers — TOP500 All top-500 supercomputers (including Fugaku) run Linux 100% Public Cloud (AWS / Azure / GCP) Linux is widely used for cloud servers 90% Web Servers (entire internet) Foundation for Apache, Nginx, and other server software 80% Smartphones (Android is Linux-based) The rest is iOS (28%). Android's kernel is Linux. 70% Embedded Devices (appliances, routers, cars) Smart TVs, smart fridges, Tesla in-car systems, routers 60% Desktop PCs (personal use) Windows 70% · macOS 18% · Linux 4% 4% 0% 100%
Fig. 2: Linux is widely used outside the desktop, especially in servers, cloud, and embedded systems.

Many web servers, the TOP500 supercomputers, Android phones, home routers, car navigation systems, robot vacuums — Linux keeps the world running in places you never notice.

Major distributions

Ubuntu is the most beginner-friendly choice. It has tons of documentation, Japanese and English guides are easy to find, and it's widely used with WSL and in the cloud. Debian is stability-focused; Fedora is for people who want to try new technologies early; Arch Linux is for advanced users who like to build things themselves. Don't overthink it at the start — just start with Ubuntu and get comfortable with commands and file navigation.

  • Ubuntu: popular with beginners; great for desktop use
  • Debian: stability-focused; widely used as a server OS
  • Fedora: adopts new technology quickly
  • Arch Linux: advanced users; the joy of building from scratch
  • Raspberry Pi OS: designed for the Raspberry Pi mini-computer

Pitfalls to watch out for

3 things beginners often mix up
  • Confusing "Linux" with a "distribution." Saying "I use Ubuntu" is precise; "I use Linux" is vague.
  • Windows and Mac software won't run directly on Linux. Use Linux-native apps or compatibility software like Wine.
  • Don't overwrite your main PC straight away. Try it in a virtual machine (VirtualBox) or via USB boot first.

How will this help you in the future?

Servers, cloud, embedded systems, AI development — Linux is the standard environment in every one of these fields. When engineers open a terminal at work, Linux commands fill the air. Getting comfortable with Linux is your biggest weapon if you're headed toward any IT career.

Learning Linux lets you see a computer not as "a box that opens apps" but as "a tool you control with commands." Reading logs, changing permissions, installing programs, starting a server — these skills are the foundation for publishing a website, developing AI, and studying security.

Things you can do today

Get started in 3 steps
  1. On Windows, enable WSL (Windows Subsystem for Linux). On Mac, Linux-style commands already work in the terminal.
  2. Try typing ls, cd, and pwd to navigate files and folders.
  3. Once you're comfortable, install Ubuntu in VirtualBox and experience the desktop version.

Summary

Linux is a free OS powering servers, smartphones, and appliances worldwide. The biggest difference from other OSes is that the source code is public and anyone can modify it. For starters, just knowing the name is enough. Try WSL or Ubuntu and the world of engineering will feel a whole lot closer.

Related articles

NextWindows vs. Linux: What's the Difference? RelatedLet's Install Ubuntu RelatedLinux Command Basics: Terminal 101 RelatedWhy Engineers Use Linux
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