No matter how powerful the components inside your computer are, you need a way to interact with them. This interaction is called input/output (I/O). The most common types of I/O in PCs are:
Monitor - The monitors the primary device for displaying information from the computer.

Input/Output card is a  board in your PC with a serial or parallel port that allows you to connect peripherals to your computer. I/O cards can also have multiple serial or parallel ports or a combination of both.

Keyboard - The keyboard is the primary device for entering information into the computer.

Mouse - The mouse is the primary device for navigating and interacting with the computer.

Removable storage - Removable storage devices allow you to add new information to your computer very easily, as well as save information that you want to carry to a different location.

Floppy Disk- The most common form of removable storage, floppy disks are extremely inexpensive and easy to save information to.
CD-ROM- CD-ROM (compact disc, read-only memory) is a popular form of distribution of commercial software. Many systems now offer CD-R (recordable) and CD-RW (rewritable), which can also record.

Flash memory - Based on a type of ROM called electrically erasable programmable read-only memory (EEPROM), Flash memory provides fast, permanent storage. Compact Flash, Smart Media and PCMCIA cards are all types of Flash memory.
DVD-ROM - DVD-ROM (digital versatile disc, read-only memory) is similar to CD-ROM but is capable of holding much more information.

Motherboard - This is the main circuit board that all of the other internal components connect to. The CPU and memory are usually on the motherboard. Other systems may be found directly on the motherboard or connected to it through a secondary connection. For example, a sound card can be built into the motherboard or connected through PCI.

Power Supply- An electrical transformer regulates the electricity used by the computer.

Hard Disk- This is large-capacity permanent storage used to hold information such as programs and documents.

Operating System - This is the basic software that allows the user to interface with the computer.

Integrated Drive Electronics (IDE) Conller - This is the primary interface for the hard drive, CD-ROM and floppy disk drive.

Peripheral Component Interconnect (PCI) Bus - The most common way to connect additional components to the computer, PCI uses a series of slots on the motherboard that PCI cards plug into.

SCSI- Pronounced "scuzzy," the small computer system interface is a method of adding additional devices, such as hard drives or scanners, to the computer.

AGP- Accelerated Graphics Port is a very high-speed connection used by the graphics card to interface with the computer.

Sound Card- This is used by the computer to record and play audio by converting analog sound into digital information and back again.

Graphics Card- This translates image data from the computer into a format that can be displayed by the monitor.