RAM, that refers to Random Access Memory, is a computer storage media which could be accessed much more quickly than a hard drive, simply because the data can be read randomly, skipping the bytes before the needed information is reached. On a server, the RAM is used to load scripts and web applications when they are executed, so the more RAM you can use, the more applications you shall be able to run concurrently and the more people will be able to surf your sites without effect on the site’s/server’s performance. Different from a disk drive, however, the RAM is used for temporary storage purposes, because the information is lost once the power is shut off. In case you use a shared web hosting account, the physical memory your scripts could use may be limited and could change based upon what the some other clients on the same machine use. Through a virtual or a dedicated server, alternatively, you'll have a guaranteed amount of RAM which will not be used by others even if you do not use it at a certain time.