Memory is the component that your computer uses to temporarily store data so that it can access it quickly. The most common type is called RAM, which stands for random access memory, and it comes in the form of chips mounted onto long strips called dual inline memory modules, or DIMMs, that are attached to the motherboard. Because these DIMMs can be easily removed and swapped, it's possible to upgrade the amount of RAM your computer has to improve its performance. However, if your computer's running without any problems, you may already have all the memory that you need.
To help you decide if you need to add more memory to your computer, please read this short list of performance signs to look out for in your machine:
Almost all modern computers should respond instantly when you click on an icon to launch a program. If there is a delay of more than a second or two, this is a sign that your operating system is using too much of your system's memory
Check in Task Manager on Windows, Activity Monitor on a Mac, or type “vmstat” into a Linux terminal, and this will tell you what percentage of your memory is being used. Be aware that the more programs you have running at the same time, the higher your memory use will be, so it's best to test it when you first load your operating system to get the base usage levels.
Unless you're using a very resource-heavy program, such as an animation program or a graphical suite, your computer should be able to run several programs without any noticeable loss of performance. For instance, if you're unable to run a word processor, a Web browser and a media player simultaneously, this is a sure sign that your computer is running out of memory.
If you're running a 32-bit Windows or Linux system, the maximum amount of RAM that you'll be able to use is 4 GB. Adding any more than 4 GB will not be recognized and might cause a startup error. For most 64-bit systems, the maximum is 512 GB.