RAM is Random Access Memory, It is used by browsers, games, and almost every application on the computer. When your computer is shut-down, all the data on the RAM is deleted, making it convenient for holding files you do not need permanently. You can buy RAM off many websites, for example, Newegg, Amazon, TigerDirect, and many more. Choosing the right amount of RAM is based on what applications you plan on running, and I suggest you look at the solution I added. I currently have 16GB of RAM, but you can do fine with just 8GB or even 6GB. I would not recommend getting lower than 4GB.