The computer has many parts, but the most important parts are:

1. Processor
   
2. Memory
   
3. Input and output devices
   
4. Storage
   

Processor: (CPU, for Central Processing Unit) is the computer's brain. It allows the processing of numeric data, meaning information entered in binary form, and the execution of instructions stored in memory to convert them into useful information.

The processor is like the brain of the computer; it organizes and carries out instructions that come from either the user or the software.

In a PC, the processor usually consists of one or more microprocessors or chips. The microprocessor is plugged into the computer´s motherboard which is a rigid rectangular card containing the circuitry that connects the processor to the other hardware. There are other internal devices you can find there like video cards, sound cards, modems, net cards, etc.

Memory: Every computer comes with a certain amount of memory, usually referred to as main memory or RAM(random access memory). Data is written to and read from this memory. You can think of main memory as an array of boxes, each of which can hold a single byte of information. A computer that has 1 megabyte of memory, therefore, can hold about 1 million bytes (or characters) of information.

The most important thing to remember about RAM is that it is volatile, so it needs a constant supply of power. When you turn off a computer, everything in RAM disappears. Thus, you should save your data files to a storage device frequently

One of the most important factors affecting the speed and power of a computer is the amount of RAM it has.

Today´s personal computers commonly have at least 2 billion bytes of random access memory (or 2 Gigabytes)

Computers use other types of memory, too. Examples are read-only memory (ROM), which permanently stores instructions that the computer needs to operate; flash memory, like the kind used in digital cameras to store images; and cache memory, which helps the CPU retrieve data and instructions more quickly.