What Linux Is and Why Servers Use It

You may go your whole life without running Linux on your laptop — and yet almost every website you open, including example.com when you type it into your browser, is sent to you by a computer running Linux. It quietly runs most of the internet, and you've been using it through other people's computers for years without knowing.

Linux is an operating system — the master program that runs a computer and lets everything else run on top of it, the same job Windows does on a PC or macOS does on a Mac. What sets Linux apart is that it's free for anyone to use and that its inner workings are public, so anyone is allowed to look at how it's built and change it. That single fact is why it ended up everywhere.

You want a personal laptop to click around on→Windows, macOS, or Linux — your choice

You want polished apps and a familiar desktop→Windows or macOS, usually

You're running a server that answers requests all day→Linux, nearly always

What is Linux?

Linux is an operating system, just like Windows and macOS from the last topic. Its core job is the same as theirs: manage the hardware, run programs, and hand each program the memory, storage, and processor time it needs. To the computer underneath, Linux is simply another OS doing that work.

The difference is in who owns it and who's allowed to change it. Windows belongs to Microsoft and macOS belongs to Apple; both are kept private, and only those companies can alter what's inside. Linux belongs to no single company. It's free to download and use, and the instructions it's built from — its source — are public for anyone to read and improve.

Think of Linux less like a product you buy and more like a public road system. No one company owns the roads; they're built and maintained by many people, anyone is free to build a house or a shop alongside them, and precisely because they're shared and open, they end up running through almost everywhere. Linux spread the same way — but a road only carries traffic, while an operating system runs entire computers, so leave the roads there and we'll talk about the real thing.

Why Do Servers Run Linux?

A server, as the network chapters will cover in full, is just a computer that runs all the time waiting to answer requests — the machine that sends you example.com when you ask for it. The people who run those machines reach for Linux again and again for a handful of down-to-earth reasons.

It costs nothing to install. When you're running not one computer but thousands of them in a data center, an operating system that's free to copy onto every machine saves real money compared with paying a per-computer license.

It runs without a screen. A server in a data center has no monitor, keyboard, or mouse attached — Linux is built to run perfectly well with nothing but a network connection, controlled from far away, which is exactly what a room full of faceless machines needs.

It's steady and easy to automate. Linux can run for months without being restarted, and because everything in it can be driven by typed instructions rather than mouse clicks, one person can set up and manage a thousand identical servers by writing the steps down once. That last part is the whole basis of the cloud and the deep-dive courses that follow this one.

What Does "Open Source" Mean?

The word for software whose inner instructions are public is open source — the source is open for anyone to read, copy, and change. Linux is the most famous example, but the idea is bigger than Linux: a great deal of the software running the internet is open source.

The payoff of opening the source is people. When thousands of programmers around the world can all see how something works, they spot problems, fix them, and add improvements that everyone then shares. Over decades, that steady stream of many hands is what made Linux reliable enough to trust with the world's servers — not a marketing budget, but openness.

Why This Course Leans on Linux From Here

From this point on, when an example needs a specific operating system, this course will usually pick Linux. That isn't a verdict that Linux is better than Windows or macOS — for a personal laptop, any of the three is a fine choice. It's simply that servers, the cloud, and nearly every course you might take after this one assume Linux.

You won't need to install it or type a single command to follow along. Leaning on Linux just means the examples match the world the later courses live in — so the vocabulary you build here is the vocabulary you'll meet again the moment you go deeper.