No matter how much memory your computer has, it never seems to be quite enough...

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THE ROLE OF MEMORY IN THE COMPUTER
People in the computer industry commonly use the term "memory" to refer to RAM (Random Access Memory). A computer uses Ram to hold temporary instructions and data needed to complete tasks. This enables the computer's CPU (Central Processing Unit), to access instructions and data stored in memory very quickly. A good example of this is when the CPU loads an application program - such as a word processing or page layout program -into memory, thereby allowing the application program to work as quickly and efficiently as possible. In practical terms, havingthe program loaded into memory means that you can get work done more quickly with less time spent waiting for thecomputer to perform tasks.

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THE DIFFERENCE BETWEEN MEMORY AND STORAGE
People often confuse the terms memory and storage, especially when describing the amount they have of each. The term memory refers to the amount of RAM installed in the computer, whereas the term storage refers to the capacity of the computer's hard disk. To clarify this common mix-up, it helps to compare your computer to an office that contains a desk and a file cabinet.The file cabinet represents the computer's hard disk, which provides storagefor all the files and information you need in your office. When you come in towork, you take out the files you need from storage and put them on your desk for easy access while you work on them. The desk is like memory in thecomputer: it holds the information and data you need to have handy whileyou're working.

Consider the desk-and-file-cabinet metaphor for a moment. Imagine what it would be like if every time you wanted to look at a document or folder you had to retrieve it from the file drawer. It would slow you down tremendously, not to mention drive you crazy. With adequate desk space - our metaphor for memory - you can lay out the documents in use and retrieve information from them immediately, often with just a glance.

Here's another important difference between memory and storage: the information stored on a hard disk remains intact even when the computer is turned off. However, any data held in memory is lost when the computer is turned off. In our desk space metaphor, it's as though any files left on the desk at closing time will be thrown away.

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MEMORY AND PERFORMANCE
It's been proven that adding more memory to a computer system increases its performance. If there isn't enough room in memory for all the information the CPU needs, the computer has to set up what's known as a virtual memory file. In so doing, the CPU reserves space on the hard disk to simulate additional RAM. This process, referred to as "swapping", slows the system down. In an average computer, it takes the CPU approximately 200ns (nanoseconds) to access RAM compared to 12,000,000ns to access the hard drive. To put this into perspective, this is equivalent to what's normally a 3 1/2 minute task taking 4 1/2 months to complete!

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(info provided from the Ultimate Memory Guide -Kingston)