Nearly every computer has an operating system. In fact, if you’re reading this article, there’s a pretty good chance you’re using one right now. There are billions of operating systems installed on computers all over the world, and 99% of the people who use them don’t have any idea what one is.

Apple’s OS X is an operating system. Microsoft Windows is also an operating system. So is Android and iOS. There are operating systems inside game consoles, tablets, mp3 players and sometimes even cars.

The simplest way to explain an operating system is this: it’s what allows you to communicate with your computer’s hardware. Chances are, your computer has a hard drive and a video display, mouse and keyboard. You might even have a printer.

All of those devices are hardware. They are manufactured electronic devices made of physical stuff like aluminum, silicon and plastic. This differs from software, which is a set of electronic signals that contains instructions and data for a computer to process. Operating systems in PCs are software.

When hardware is made, manufacturers design it so certain kinds of signals will make it work. Certain amounts of electricity in certain patterns will make a hard drive look for data in a certain place on the disc. Different signals will make your video display that data in red letters instead of yellow letters. Your keyboard and mouse send signals so the rest of your computer will know whether the mouse arrow is moving up or down, or whether you pressed ‘k’ or ‘r’ when you were typing your business letter.

So you’ve got this massive number of signals flying all over the inside of your computer, all produced by your computer’s hardware. How is anyone going to make sense of all that? What are you supposed to do? Attach wires from your keyboard to your video display and hope something actually shows up when you start typing? That’s where an operating system comes in.

The operating system makes use of a very important piece of hardware called your central processing unit, or CPU. You probably bought your computer because the ad said it had a fast processor. That’s your CPU. It’s a very dense package of high-performance transistors and circuits that knows how to make a lot of simple decisions and do simple math problems very fast: billions of times per second. Almost everything that happens in your computer happens because of instructions sent from or received by your CPU, and those instructions are usually carried back and forth by your operating system.

The operating system uses your processor, or CPU, to collect all the signals from all the pieces of hardware on your system and make sense of them. It takes the signal produced by your mouse that says “move up” and then tells the video display to move the arrow “up” on the screen. It takes the signal produced by your keyboard that you pressed a letter ‘d’ and tells the video display to put a ‘d’ on the screen.

Every time your computer’s hardware does something, whether it’s your disk drive, USB printer, wi-fi networking system or even sometimes the power button, it’s because your operating system gave it the correct instructions, or understood the signals that piece of hardware sent to the computer.

The core of Linux is an operating system. It’s commonly referred to as a “kernel” which is just another name for the basic software that talks to your computer hardware. The Linux kernel works on many different kinds of computers, from large web servers all the way to very small smartphones.

Each kernel has built-in sections that can talk to different kinds of hardware. These “sections” of the kernel are called “drivers.” A driver is a piece of software, or a set of instructions that talks to a specific kind of device, like a Seagate hard drive, or a Linksys network card. If all the right drivers are available, your operating system, or “kernel” can make all the different pieces of hardware in your computer work correctly.

But there’s much more to Linux than just the kernel. In fact, if you use Linux, once everything is set up correctly, you’ll probably never notice the kernel, aside from the occasional update. What you will notice is the amazing selection of other software you can run on your Linux computer. We’ll cover some of those applications in future articles.