RAM stands for random access memory. It is important that you understand what it is and what it does before you go adding it to your computer. It does not matter if you are upgrading your computer or adding additional memory. Most people think the more RAM the better and that can be true up to a certain point. The choice to add more RAM really depends on what programs you intend to run on your computer.
Random access memory is needed for running your programs faster. Your hard drive is actually very slow when it comes to deciphering information. Most processors are very fast and your hard drive just cannot keep up with it. The RAM is used to hold certain information until your hard drive can store it. If you do not have enough RAM then your computer is going to be super slow. If you are running a program that requires a certain amount of RAM and you do not have enough, your hard drive will try to catch some of the memory. That in turn makes your computer slow.
Most system requirements need your computer to have at least 2GB of RAM. That is usually enough RAM for a casual user or a student. It really depends on what programs that you want to run as to how much RAM you should have. For a moderate user who likes to download music and movies 4GB to 6GB should be enough. If you run a business or you love to play games and download lots of movies then 8GB is going to be what you want. However, keep in mind that more RAM equals more money. When you step up the RAM you are getting into some big bucks. So really evaluate your needs before you spend money on something you may not even need.