You Need to Know About Computer Hardware:

Computer hardware is the physical parts or components of a computer, such as the monitor, keyboard, computer data storage,graphic card, sound card and motherboard. that can be installed inside, and connected to the outside, of a computer. Wikipedia

List of Computer Hardware

Here are some common individual computer hardware components that you'll often find inside a modern computer. These parts are almost always found inside the computer's housing:

Motherboard

Central Processing Unit (CPU)

Random Access Memory (RAM)

Power Supply

Video Card

Hard Drive (HDD)

Solid-State Drive (SSD)

Optical Drive (e.g. BD/DVD/CD drive)

Card Reader (SD/SDHC, CF, etc.)

Here is some common hardware that you might find connected to the outside of a computer, although many tablets, laptops, and netbooks integrate some of these items into their housings:

Monitor
Keyboard
Mouse
Battery Backup (UPS)
Flash Drive
Printer
Speakers
External Hard Drive
Pen Tablet

Here are some less common individual computer hardware devices, either because these pieces are now usually integrated into other devices or because they've been replaced with newer technology:

Sound Card
Network Interface Card (NIC)
Expansion Card (Firewire, USB, etc.)
Hard Drive Controller Card
Analog Modem

Scanner
Projector
Floppy Disk Drive
Joystick
Webcam
Microphone
Tape Drive
Zip Drive

The following hardware is referred to as network hardware, and various pieces are often part of a home or business network:

Digital Modem (e.g. Cable Modem, DSL Modem, etc.)
Router
Network Switch
Access Point
Repeater
Bridge
Print Server
Firewall

Network hardware isn't as clearly defined as some other types of computer hardware. For example, many home routers will often act as a combination router, switch, and firewall.

In addition to all the items listed above, there's more computer hardware that I like to call auxiliary hardware, of which a computer might have none, or several, of some kinds:

Fan (CPU, GPU, Case, etc.)
Heat Sink
Data Cable
Power Cable
CMOS Battery
Daughterboard

Some of the devices listed above are called peripheral devices. A peripheral device is a piece of hardware (whether internal or external) that isn't actually involved in the computer's main function. Examples include a monitor, video card, disc drive, and mouse.

Troubleshooting Faulty Computer Hardware

Computer hardware components individually heat up and cool down as they're used and then not used, meaning that eventually, every single one will fail.

Some may even fail at the same time.

Fortunately, at least with desktop computers and some laptop and tablet computers, you can replace the non-working piece of hardware without having to replace or rebuild the computer from scratch.

Here are some resources you should check out before you go out and purchase a new hard drive, replacement RAM sticks, or anything else you think may be going bad:

In Microsoft Windows, hardware resources are managed by Device Manager. It's possible that a "faulty" piece of computer hardware is really just in need of a device driver installation or update, or for the device to be enabled in Device Manager.

Hardware devices won't work at all if the device is disabled, or may not be running properly if the wrong driver is installed.