the difference between ram and rom is: When you power off your computer the data stored in RAM is deleted. ROM is a type of non- volatile memory. Data in ROM is permanently written and is not erased when you power off your computer.
What is RAM actually do?
Other than the specific applications that hog your RAM, if you think bumping your RAM from 3GB to 8GB is going to increase the speed of a regular application-like a video game—you should think again. The only thing that additional RAM does is allow your computer to do more things at once, not actually make it faster.