RAM=Random Access Memory, used for fast swapping of data on computer Processor= a small chip on the motherboard performing millions+calculations a second. your computer uses ram all the time to keep background apps open, and to basically run everything. your computer uses your processor when you do graphic intensive or calculation intensive things, such as gaming, video converting, multiple things at once, like running Photoshop, a video encoder, your internet browser, and watching a movie. now if you want to know which to upgrade, it depends on the current status of your computer, and your aim of the upgrade.