# Linux Introduction — Linux Command Line Fundamentals

Source: https://www.skillbyai.com/en/linux/linux-intro

> Learn what Linux is, how the kernel differs from distributions such as Ubuntu and Fedora, and the everything-is-a-file idea.

## What is Linux?

**Linux** is a free, open-source **kernel** originally created by Linus Torvalds in 1991. Combined with system tools and a package manager, it forms a complete operating system that powers servers, phones (Android), and supercomputers.

## Distros at a glance

A **distribution (distro)** bundles the Linux kernel with software and a package manager. **Ubuntu/Debian** are beginner-friendly and use `apt`. **Fedora/RHEL/CentOS** favor `dnf`/`yum`. **Arch** is minimal and rolling-release.

## Everything is a file

A core Linux philosophy: devices, processes, even network sockets are represented as files under `/dev`, `/proc`, and `/sys`. This uniformity is why so many tools compose well together.