RAM, that is short for Random Access Memory, is a computer storage media which can be accessed way quicker than a hard drive, as the information can be read randomly, skipping the bytes before the needed information is reached. On a web server, the RAM is employed to load scripts and web apps after they are executed, so the more RAM you are able to use, the more apps you'll be able to run concurrently and the more people will be able to look through your sites without effect on the site’s/server’s general performance. Different from a disk drive, however, the RAM is employed for non permanent storage purposes, because the info is lost when the power is shut off. If you use a shared web hosting account, the physical memory which your scripts could use may be limited and can change depending on what the other customers on the same machine use. Using a virtual or a dedicated hosting server, on the other hand, you will have a set amount of RAM that won't be used by anybody else even if you do not use it at a particular time.