Linux is not a single operating system but a family of distributions (distros) built around the Linux kernel. Popular choices include Ubuntu, Fedora, Debian, and Arch Linux. Each distro bundles the kernel with a set of tools, a package manager, and often a desktop environment.

The Linux kernel manages hardware resources (CPU, memory, storage, and I/O) and exposes them to user-space programs through a set of system calls. Everything you do on a Linux system ultimately flows through the kernel.

To check which kernel version your system is running, open a terminal and type:

uname -r

A typical Linux system layers from hardware up through: kernel → system libraries (glibc) → shell (bash/zsh) → utilities (coreutils) → desktop environment or server software. Understanding this stack helps you diagnose problems and optimise performance.