Inside A Computer

Memory - This is very fast storage used to hold data. It has to be fast because it connects directly to the microprocessor. There are several specific types of memory in a computer:
Random-access memory (RAM) - Used to temporarily store information that the computer is currently working with
Read-only memory (ROM) - A permanent type of memory storage used by the computer for important data that does not change
Basic input/output system (BIOS) - A type of ROM that is used by the computer to establish basic communication when the computer is first turned on
Caching - The storing of frequently used data in extremely fast RAM that connects directly to the CPU
Virtual memory - Space on a hard disk used to temporarily store data and swap it in and out of RAM as needed

Defining a PC
Here is one way to think about it: A PC is a general-purpose information processing device. It can take information from a person (through the keyboard and mouse), from a device (like a floppy disk or CD) or from the network (through a modem or a network card) and process it. Once processed, the information is shown to the user (on the monitor), stored on a device (like a hard disk) or sent somewhere else on the network (back through the modem or network card).
We have lots of special-purpose processors in our lives. An MP3 Player is a specialized computer for processing MP3 files. It can't do anything else. A GPS is a specialized computer for handling GPS signals. It can't do anything else. A Gameboy is a specialized computer for handling games, but it can't do anything else. A PC can do it all because it is general-purpose.

Computer's Motherboard