ROM stands for read only memory. RAM stands for random access memory. Things saved to ROM will not be erased after you turn off the computer. If you turn off the computer before saving, whatever you were working on will be lost. Anything saved on RAM but not to a ROM will be lost. Virtual memory allows you to have multiple tasks/programs at one time. Without it we would not be able to run many programs at once. Casching lets you check you memory more quickly rather than manually entering it. All these things help you run your computer and save files with ease.


Sources From:
http://www.howstuffworks.com/