What's Inside Your Computer? A Plain-English Guide to PC Parts

Updated September 28, 2026 · By Shannon Jones, Roo Tech Services

The short answer: Every PC is built from a handful of main parts. The motherboard connects everything, the CPU does the thinking, RAM holds what you're working on right now, the hard drive or SSD stores your files, and the graphics card (or the CPU's built-in graphics) draws what you see on screen. A power supply and fans keep it all running.

Most of us use a computer every single day, whether it be for work, school, checking social media or just for relaxing to play a game or watch a video, but many of us never stop to think how these complex machines work. Knowing this isn't a necessity, since you can always reach out to your local IT guy for help, but it can give you a better understanding of what exactly is going on with your system. So let's take a look at what makes up a PC and how it all fits together to allow you to do everything we mentioned above and much, much more. Don't worry, we won't get too technical. We'll just review the main parts and what each one does. Here we go!

The motherboard

The first component we are going to talk about, arguably the most important part, is the motherboard. Your motherboard is the component of your PC that all the other components connect through. Everything, from your system's memory, hard drive, and graphics card, plugs into your motherboard, and that allows these components to all work together to make your system work. This is also the component that houses the brains of the operation, your CPU, or Central Processing Unit. The motherboard also houses the different ports that everything connects to, like the USB ports that you plug a keyboard, mouse or flash drive into, and your monitor connections, usually via an HDMI, DVI or VGA cable. There are also DisplayPort cables, but we won't go into those here. Think of the motherboard as the skeletal structure of the PC: without it, everything else would just fall apart.

The CPU (processor)

Another important component is the CPU. The CPU handles all of the calculations and instructions that you give to your computer every time you type on the keyboard or click on an application to run. If you have ever taken the side panel off your computer, you have probably seen a large heat sink with a fan attached to it. This heat sink usually sits on top of your CPU and helps to cool it down. Some systems, especially gaming systems, use water cooling instead: water runs over a copper plate that draws heat away from the CPU, then through a radiator that cools the water back down. Most CPUs have a thermal threshold that will shut your PC down if the CPU gets too hot.

RAM (memory)

Much like us, our PCs can temporarily remember things to help them run faster. This is where a system's RAM or memory comes in. RAM, or Random Access Memory, is what your CPU uses to be able to run commonly used programs quickly by storing the information needed to run them in a short-term data storage location. This memory is cleared out each time you reboot your PC. Ever wondered why your IT guy asks you to turn your PC off and back on again? This is part of the reason. When a program starts "acting up," it could potentially be that something stored in memory was not accessed properly, and 9 times out of 10 a restart fixes it.

Storage: hard drives and SSDs

When you finish working on a project and you click that save button, this is where your system's hard drive comes in. The hard drive is what stores all of your files, pictures, music and pretty much anything your system runs. Most systems today come with an SSD, or solid state drive. The benefit to these drives is that they have no moving parts, so they are less prone to the wear and physical failures of an older mechanical hard drive with spinning disks. Another benefit is that because these drives are just memory chips that can be read almost instantly, they tend to be much faster and greatly increase performance. They do cost a bit more per gigabyte, but prices are constantly decreasing on storage.

The graphics card (GPU)

Of course, to do anything with any of this, you need to have a monitor to view it all on, and this is where your system's video card comes in. Your GPU, or Graphics Processing Unit, is what takes care of this for you. Your video card is almost like a little mini computer of its own, as it has a GPU which, much like a CPU, is the brains of your card and handles all of the calculations and processing associated with graphics. It has its own memory as well. Some CPUs handle your graphics for you. This is commonly called integrated or on-board graphics. What this means is that rather than a dedicated video card, your CPU processes all of your graphics. This can greatly decrease the overall cost of your PC and works great if your main functions on your PC are checking email, working within Microsoft Office applications or posting to social media. However, if you intend to play games, especially AAA titles, or work with Adobe Creative Cloud programs like Photoshop, a dedicated graphics card is highly recommended.

Everything else: fans, power supply and more

Other components you may find in your PC are sound and network cards, but often these are just built into the motherboard much like your USB ports. There are also fans which help to keep all of these components cooled down as they all heat up when your system is running. Then, of course, there is your power supply, which most of the cables in your PC run back to and which regulates the amount of power that is required for each component. Outside of that you have your keyboard, mouse and monitor.

Putting it all together

There you have it, all of your PC's main components broken down and explained. Hopefully you now have a better understanding of the inner workings of your PC, which will help you narrow down the cause when something goes wrong. For instance, if your PC turns on but you see nothing but a black screen, chances are it has something to do with your video card, either a cable came loose or perhaps your card has died and you need a new one. It could be something else, but this gives you a good starting point, and if nothing else, it will give you more information to pass along to your IT guy to help fix the problem.

So don't be afraid to open up your computer case (shut it down and unplug it first), take a look around inside, and familiarize yourself with all of your system's components. Maybe even contact your IT support company and ask them to give you a walk-through of each part. The more information you can give your technician, the easier it will be for them to locate the exact issue, get it fixed for you, and get your system back to doing what it does best: working.

Frequently asked questions

What are the main parts of a computer?

The main parts are the motherboard, the CPU (processor), RAM (memory), storage (a hard drive or SSD), the graphics card or the CPU's built-in graphics, the power supply, and cooling fans. Your keyboard, mouse and monitor connect to it from the outside.

What's the difference between RAM and storage?

RAM is short-term memory your computer uses for whatever is running right now, and it's cleared when you restart. Storage, meaning a hard drive or SSD, keeps your files and programs long-term, even when the computer is off.

Is an SSD better than a hard drive?

For most people, yes. An SSD has no moving parts, so it's much faster and less prone to physical failure than a spinning hard drive. It costs a bit more per gigabyte, but prices keep coming down.

Why does restarting my computer fix so many problems?

Restarting clears out RAM, so a program that got stuck on something stored in memory gets a clean start. It won't fix everything, but it solves a surprising number of everyday glitches.

Do I need a dedicated graphics card?

Not for email, Microsoft Office and web browsing. The graphics built into most CPUs handle that fine. A dedicated graphics card is worth it for gaming, video editing, or design work in programs like Photoshop.

Need help with your computer?

Roo Tech Services is a veteran-owned IT company in Knoxville, TN. If a computer at your business is acting up, learn about our custom IT solutions, book a free consultation, or call 865-332-0008.

About the author: Shannon Jones is the founder of Roo Tech Services, a veteran-owned IT company in Knoxville, Tennessee. He served in the U.S. Marine Corps from 2000 to 2004, including in Iraq in 2003, and is Fortinet NSE 3 certified.